Bonanno wasn't the one who proposed Valachi, so he wasn't the sponsor in that sense (Petrilli originally proposed him), but he was selected for the godfather role. Only other time I've seen that was Rocco Scafidi's induction in Philly where they did the same finger game and even though Joe Scafidi proposed him, Domenico Pollina was randomly selected as godather. Bonanno denies the story but obviously wanted to distance himself from Valachi. It's sort of like Valachi's claim about meeting Joe Profaci at the Pelham Parkway spot and Profaci explaining the history to him. It doesn't really make sense for Profaci to be there and we have doubts but I don't see why Valachi would deliberately lie about it. Strangely, Valachi says in the Real Thing that Profaci was also at his induction ceremony.
In Sicily there have been inductions presided over by the boss of another Family, like Agostino Coppola whose ceremony was presided over by Gaetano Badalamenti of Cinisi but Coppola was being made into the Corleone Family or Giovanni Brusca's induction which was presided over by the Corleone leadership even though he was made into the San Giuseppe Jato Family. The "godfather" thing also brings to mind John Stanfa's visit to Caccamo in the early 1980s where Nino Giuffre was allowed to select Stanfa as his godfather for the induction ceremony -- Stanfa was likely made in Caccamo originally but at that time he was a Philadelphia member. John Misuraca also proposed a few members into the San Jose Family even though he was a Colombo member and Bonanno underboss Frank Garofalo attended a San Francisco ceremony as the guest of honor. I'm skeptical of Bill Bonanno's claim that his induction was basically a Commission meeting of bosses but there is some fluidity with that stuff, or at least there used to be, where inductions can involve members of other Families playing roles. These aren't rival gangs but members of the same brotherhood and all of the Families used to be much more intertwined.
It doesn't seem Valachi got to know many "real" dyed-in-the-wool Bonanno members during the war. He spent a lot of time with Domingo and DiBenedetto and would have met a bunch of others at Maranzano's office and the larger meetings that were held but most of the guys he knew were from the Lucchese side of the alliance. He had very little info on the Bonannos when he flipped even though plenty of contemporary members had been around in the early 1930s.
Valachi had a dizzying career in the mafia for a Neapolitan with no connection to tradition.
Judge for yourself. Valachi was closely acquainted with the bosses Maranzano, Gagliano and Lucchese, was close to Vito Genovese. He became related to the respected Reina family, with these introductory information, if he had stayed in the Gagliano family, he could have risen to the rank of captain. In Maranzano's retinue, he played an important role, was appointed a soldier personally under the boss, which is a great honor. In the mafia, it is very honorable to be under the boss, such people are often more influential than captains.
In the Genovese family, Valachi's status fell sharply, but even there he was connected to very influential people. He had a long history of relations with Vito Genovese, a very influential figure. Since the crew was huge, Valachi was essentially a sub-captain at one time, helping capo Anthony Strollo manage part of the crew. All of the above makes Valachi more than just your average soldier.
He proposed at least four people into the Genovese too. The Pagano brothers, Vinnie Mauro, and his nephew Siano. He takes credit for recruiting a lot of guys who joined in the early 1930s too, most of which ended up with the Luccheses but some spent time with him in the Bonannos and ended up Genovese.
Like almost everyone who has cooperated or written a memoir, he talks himself up and criticizes other people but I think a majority of basic facts he tells are true or to the best of his recollection. I'm guessing Valachi's disposition and reputation were the biggest factors in how quickly he became accepted by important people -- he was an uneducated street guy but in the video of his testimony he comes across highly intelligent and we know his toughness was no joke. His early history in East Harlem can't be ignored as he was known by important people from a young age then he did time with well-connected people, survived a prison stabbing without cooperating, etc.
His direct mafia association happened quickly but he'd been doing the right thing in the right neighborhood and meeting the right people for a long time, then he dropped everything to fight a major mafia war he had no personal interest in and did everything that was asked of him, especially murder. It's not like he was a random Italian mugger picked up off the street and Maranzano gave him a machine gun and said "Go, fight Joe the Boss," he was actually making himself "somebody" in the network for years without even realizing it himself.
A detail he doesn't mention in any of his narratives is that his brother-in-law was Gambino member Salvatore Bonfrisco. Bonfrisco married another one of the Reina daughters, so they were married to sisters. He did identify Bonfrisco as a Gambino member in his FBI interviews but that's the extent of it as far as I know.