Yes, I wouldn't say Waterstones is GC. From what I can see, they fired an employee for making public statements that she intended to rip up books and otherwise make it difficult for readers to buy certain authors because she didn't like the authors' views.
As others have said, I'd expect Waterstones to sack her if it were the other way around too (e.g. if she were GC and claiming to rip up trans authors books).
It's only really remarkable because trans activists have been getting away with this kind of behaviour for so long that they don't even see what's wrong with it.