You got a source on that?
He's spoken at length about his role in making each of the games, but it might be difficult for me to pull up links right now because I don't remember the individual sources for every single detail. There's also a lot of Japanese stuff that's been translated over the years that's been lost in time. If you don't trust me, maybe Masked Man or someone else who speaks Japanese can vouch for some of these sources:
SSB64 - The start of the project is discussed
here, though I think the origins of this game are pretty well-documented.
Melee - The second half of
this page says that Sakurai secretly wrote the project plan document in the summer of 1999 while publicly pretending he wasn't working on another Smash Bros.
Brawl -
"I decide what goes in the game; nobody else."
"[...]me going into solitary to write the design document[...]" - this whole article is pretty insightful.
The
Iwata Asks interview also paints a really good picture of Sakurai's role in making Brawl.
3DS/Wii U -
This entire article. Specifically, things like:
"The team knows what I want in the game"
"The team's work is all built up according to what I told them, so it's ultimately my job to make adjustments and finalize it all."
"When I'm discussing supervision work with people, sometimes upwards of 20 staffers at once," he wrote, "there's often a video camera going around to record what I said and told them to do."
"Characters' in-game balance and features are something that I'm thinking about from the start while coming up with motions," he said. "If I left that to someone else midway, that'd make things more difficult. It's faster and more accurate to just input the numbers myself than try to explain it in words to somebody."
I just don't get the impression that Sakurai's taken on any kind of diminished/advisory/backseat role over the history of the series. He's obviously not the only person working on the game, and I never said he was -- just that his involvement in SSB4 is comparable to 64, Melee, and Brawl. He's always been a control freak.