"Is this effectively hiding the entire FWR board from the rest of MN?"
Yes.
And it is because of the tone of trans threads.
When you surround yourself with fellow TERFs, your sense of what is reasonable changes. Do do not realise how this seems to others who do not share your views. You do not realise when it ties into bigotry.
You do not realise that other protected groups can and have defined the extent of expression of other protected groups (did you stand with Jews, Muslims or Christians when defining conditions of provisions of goods and services in pluralistic, well-supplied sectors?)
Meeting every 'no, not everyone sees it like that' with 'you're silencing us' just sounds like 'so you have to shut up instead, because some women are more equal than others'
Rejecting a trans topic, because you see it as a central issue and therefore indivisible from feminist chat, is the thing that has led to the ending of FWR as a real, fully participant part of MN. Because now it's gone, people might not want it back.
I think a trans topic, or a lib fem chat topic could have been excellent ideas, and was somewhat disappointed when both were rejected (the former multiple times) and taking just the contentious areas elsewhere would have kept feminism as a mainstream part of MN. But I think that chance has gone.