I've seen both. Our area has had, for a few years, mixed use zoning as a requirement. So a bunch of projects that clearly only wanted to do housing are doing what you describe: Housing and a meets minimum commercial/office effort. Notably while trumpeting "walkable" which is really code for "we don't waste land on unprofitable parking lots". So you have somewhat dense living and retail where the retail has zero parking, so the only people a business could hope to get are the people in the units immediately close by, which are not a lot, since each project seems to go for low rise housing. So you get three stories of apartments which is more dense than suburbia, but not nearly dense enough to sustain a dedicated retail presence.

But there is this mall they've effectively renovated into a "downtown", adding high rise apartments, and lots of them to the massive retail presence as well as big office buildings. Critically, also expanded to an insane degree the amount of available parking. It was a pretty failing mall (like most) and now it's doing really well, both with high occupancy for their apartments and people going there for the rather nice retail. I think this was the first project and inspired the county to decide everything will be a success if it's just mixed use, and they haven't really come around to realize that they haven't succeeded in forcing the developers to do viable mixed use by the current weak regulations.