Yeah, it's just that I've seen "Sakurai wanted Ninjara specifically" tossed around a fair bit, and I felt like that needed to be cleared up a bit.
As for the Spring Man thing, I think it's pretty simple. Sakurai asked Yabuki, Yabuki said Min Min, and Yabuki got Min Min. Out of the ensemble cast, Spring Man got the biggest marketing push, and the devs wanted to address his larger role in the marketing, even though he wasn't chosen.
Yeah, I believe you're right for that case.
Honestly, I feel like we would've gotten Min Min regardless of Yabuki's request. If we were to completely ignore the existence of said request, Sakurai only stated that he considered Min Min and Ninjara, so it seemed like Spring Man wasn't even in the running anyway.
Let's compare Min Min with Ninjara' popularity first. Both are popular, with both characters reaching the finale of the final Party Crash Bash. Obviously we wouldn't know if Min Min's victory would've given the push for certain, but it certainly was a game changer in the lore of ARMS itself, basically making Min Min the canon victor of the tournament. Official artwork of a victorious Min Min with the champion belt circled the web, which boosted her already impressive popularity even further. By the time Sakurai was looking for an ARMS fighter, Min Min was already one of the more recognizable characters outside of the boxart duo. Ninjara certainly had his fans for sure, but they paled in comparison to the Ramen Bomber.
And then we compare the two mechanically. I don't doubt that Sakurai could make a fun moveset for Ninjara, but compared to Min Min, his special abilities aren't nearly as welcoming to Smash. He's all about evasive capabilities, so he would be able to air dash safely and invisibly (which would just be an air dodge) and avoid moves instead of taking chip damage (not sure how you incorporate that in. Sakurai could probably pull it off, but it'd definitely take some creative thinking... or a counter). Then you look at Min Min: not only does she get a fun little power boost to her left arm after certain conditions are met, but she get a whole slew of moveset potential thanks to canonically using kicks. Sure, I guess you could let anyone use kicks for a small, fast pace move, but Min Min makes by far the most sense since she kicks in her own game.
So yeah, through fan popularity, creator popularity, and just pure moveset potential, it felt like Min Min was an inevitable pick.
I do feel bad for Spring Man though. He looked so happy in Min Min's trailer, only to get punched in the face. And then you see him sadly watching on in the background of the promotional poster. Better luck next time, buddy!