It has always been the HumanoidRootPart, if this change was planned then it was not announced because now every character that spawns on a server has their primarypart assigned to the Head, this not only breaks checks in games for velocity that rely on primarypart being the root but also can severely screw up any physics motion work you’re doing by applying a force to the wrong part of the body.
Expected behavior
I expect the primarypart of the character to be the HumanoidRootPart
Hi, thanks for the report! As mentioned by @xyrafrost, this has always been the R6 schema, which would be difficult to change for backwards compatibility reason.
A recent regression was introduced in the Animation Clip Editor which broke under this assumption. We are currently fixing this particular issue (see Issues with the animation editor on R6 rigs).