#33729 affected the behavior of the has_many through record creation.

Since #33729, the intermediate reflection of simple has_many through
association has `inverse_of` to the association, it causes extra through
record creation, the extra through record required valid before the
association record is saved.

https://github.com/rails/rails/blob/23125378673bcc606b274027666a126573e136f8/activerecord/lib/active_record/associations/has_many_through_association.rb#L95-L102

I think that #33729 need to more work to care about has_many through
association, that PR should be reverted to not break existing apps.