This is what generally happens when you fly in a non-union environment. IMHO, I'm thinking perhaps the the pilots were worried about company retributions if they were to air-return a full 777.
At my airline, we don't hesitate such decisions, we know the union has our back... even though our union has been pretty weak lately.
By contrast, I gather things are different at other carriers... from what I read on here and other boards.
For myself, I flew on a non-union position while on LOA last year. It seemed like every move I made as a Captain was judged and question by middle management. What a way to work. IMO, highly unsafe.
If I'm wrong in my assessment of non-union flying, feel free to correct me.