That’s a good observation. There are a number of factors that play into smoothness.
First thing, is it’s impossible to make them perfect so there is always some amount of error. The design of the yoyo makes a big difference. We think of it as each model can tolerate a certain amount of error. What the means is that each model is easier or harder to make smooth. As it turns out with physics, very generally speaking, the kind of designs people want are the same kind that don’t tolerate error very well - things like being wide and having lots of axial rim weight.
There are a number of tolerances other than the bearing post that affect smoothness as well. So the amount of error in a particular yoyo is a cumulation of different critical tolerances (the bearing post is one of the most important but not the only one).
You can have a yoyo with a damaged bearing post still be smooth if the other tolerances are good and the design has the right amount of error tolerance. Simplied, you have the amount of error a design can tolerate and then you have the actual of amount of error in a discrete sample. If there is more error than what can be tolerated, there will be vibe. If not, then smooth.
We have our Physics Doctor friend, Dirty Birdy who has done a lot of work in this area so he can do analysis of our CAD before we cut metal and let us know how tolerant of error it is. We developed general ideas over the years and are pretty good at predicting, but Dirty Birdy is using math and it’s very accurate. So now we have him do an analysis of every model before we do any cutting.