The HOA Act provision you rely on deals with max number of votes required to change the bylaws by the membership. It does not state only the membership can change the bylaws. It also says the 60% of whatever applies unless the bylaws provide a lower number, as I recall.

Since the Charter is higher in the hierarchy of OPA governing documents, short of a specific applicable court case, I will maintain the board can take control of the bylaws via the Charter.

Perhaps the board will do so and you will then have the opportunity to litigate the issue as you apparently threaten to do if that takes place.

Meantime, as a practical matter, the board is not going to try and take control of the bylaws via the Charter.