In recent years the RMT has been demanding "no compulsory redundancies" when any new franchise has been let (plus retention of guard roles etc).
This goes back to the fact that it’s a trade union so it would be rather odd for it to demand anything else.
Although the government effectively made this guarantee during the Covid emergency period (full employment with no furlough).
It's a fantasy when you have lost 20-30% of your custom and are attempting to re-size the business.
Given how tight staffing levels are in many areas, I rather suspect any redundancies will come from changes in working practices, for example ticket office closures, rather than as a result of lower passenger numbers. This should almost certainly be achievable through redeployment and voluntary redundancy for those who want it.
I would completely agree that, in situations such as that, the RMT should be focussed on ensuring there are no compulsory redundancies rather than resisting the change at all costs.