(The stock bi-metal washers will crack or loose their shape under too much pressure)

 

Well, I've been turning these engines (with stock tensioners) backwards (by hand) for over 40 years and have never seen a ruined tensioner or a cracked bi-metallic washer from doing this.
.....Actually, I've only ever seen tensioners that are ruined when they are run for many miles without oil.
.....And I've never seen a cracked bi-metallic washer on any tensioner.