I would take this with a pinch of salt.
This in fact was reported a while ago and was from a Labour source.
It is part of the slur campaign against Baroness Falkner ie she was just a trouble maker.
And it may well be that just out of self presevation MAS is playing it low key. Who wants the type of vitriol not just Labour but all the TRAs flung as Falkner.
So can see why the Guardian is spinning this.
(Of course it may also be that MAS is being a realist and knows from her experience of being cross examined at the WEC that the mean girls aren't going to give way. So long as she holds the line and doesn't let Labour try and take away the existing sex based rights that we have as women.)