It's an ever weakening stance not to declare the start of industrial action.
Bassa know they've got weak support for the strike (the percentages are irrelevant as voting Yes was thought by many to be the end in itself) and BA know they know that. Any delay just reinforces to BA that Bassa haven't the nerve to follow through as it's going to lead to their destruction.
It needs some strong heads to stand up at Kempton and tell Bassa to back down, if they want Bassa to survive.
For the good of the company and cabin crew long term, it's probably better if they don't. That would then allow the PCC to take its members forward into the 'New Fleeted' future.