I think they will when/if a manufacturer/company says it’s because of Brexit. This is the problem in that remainers want shit to happen due to Brexit because it fits their narrative. Remainer politicians and commentators are focused on it as they are desparate to change the result.
But despite the Honda Senior Vice President saying publicly that Brexit, and the Japan/EU trade deal, are not the reason for the planned closure of this plant in Swindon, remain supporters, politicians and commentators just won’t accept it. So no matter what is said or what evidence is produced, the Brexit mindset, which ever way people see it, is fixed. I despair I really do as I can’t see when this will end.