No, they aren't at 28nm. They're shipping 14nm at volume, have low-volume R&D yields of 7nm, and are building their own EUV process for 5nm and below.

Sanctioning and restricting China is most certainly going to be a catalyst for a rapid development of domestic advancements (including, of course, surreptitiously stealing it from other countries/companies). Anyone who thinks China won't be right with the top makers in a few short years is fooling themselves.