If you want to know how they work, you just have to go back a few days to when Plaid Cymru called for the devolution of welfare administration.

Their argument against devolving welfare administration was that people in Swindon (Yes, Swindon in England) would be treated differently to people in Wales.

Basically, they could save the poorest and most vulnerable people in Wales from Conservative welfare policies or at least mitigate them but won't because they can't save the English from them. Is that standing up for Wales as they claim to do?

TL;DR Labour are British nationalist red tories. The UK's and their own interests always come first, Wales' interests are probably the last thing on their mind.