A quick read seems to me to state that no, the Basel crowd did not give banks an OK to hold 2% in Bitcoin. On the contrary they've added a new rule that states it needs to be <1% (and even then should be risk weighted at 1250%).

BIS (https://www.bis.org/bcbs/publ/d545.pdf) This states that banks should in the normal course of business hold less than 1% and must report anything higher, 2% is when an additional 'penalty' applies.