The Sakurai bias thing is an unfortunate side effect of the 3DS version having a ton of imported content from Kid Icarus: Uprising. Both are 3DS games and the development team had access to all sorts of assets from that game, so it was a very convenient and fast way of putting more content in the game. The Wii U version has a lot less content from Kid Icarus, having about as much content as the Fire Emblem series.
Models were used for trophies and there are lot of recycled enemies from KIU in Smash Run (the animations and AI are nearly identical to their original appearances).
Ironically, you could say that KIU has a lot of Sakurai bias, with the game having a lot of similarities to Smash Bros. regarding gameplay, as it feels a lot like "Smash Bros. meets rail and third person shooters".
It also has:
- tons of references to other Nintendo games (making it feel a lot more like a Smash game at times)
- similar items as Smash: the most blatant is a Smart Bomb that does exactly the same thing as the Star Fox Smart Bomb in Brawl and Smash 4, with the design being the only difference
- there's also the Daybreak item that works like the Dragoon from Kirby Air Ride (and made its way into Smash 4 co-existing with the original inspiration behind it)
- collectible Idols: the same thing as Trophies from Smash, except they use animated models
- the Challenge grid: called Treasure Hunt instead and has feathers instead of hammers, otherwise it's the same thing seen in Sakurai's games since Kirby Air Ride
- boss rush that works exactly the same as Smash's All-Star and Boss Battles modes: you fight all bosses of the game and between each fight you go to a rest area that shows the bosses you've defeated so far and limited healing items
Sakurai recycles game design ideas and concepts regardless of the series he's working on. He imported a lot of KIU stuff into Smash 3DS because those worked in Smash and were easy to port. Common development practice right here: if things from previous projects work in a new one, use them.
Does anyone think one of the main reasons why Palutena was included was because her name was in many of the Japanese version of the KI titles?
Well, the series name in Japan is called Hikari Shinwa: Parutena no Kagami (Light Myth: Palutena's Mirror).
The second game wasn't released in Japan (until the VC release) and I don't think it has a Japanese title either. Kid Icarus: Uprising is called Shin Hikari Shinwa: Parutena no Kagami (New Light Myth: Palutena's Mirror).
Anyway, Palutena is the most important character after Pit in the series and fills a role similar to Peach and Zelda in their respective series. In Japan, she also happens to be the title character of the series.