To clarify, the pictured poster Caroline Kwan is an ally, not a TERF. The TERFs referred to in the title are the ones ‘protecting a very specific idea of what a woman is’
I'll repeat what I said elsewhere about this debate. You probably wonder "so what should the rules be to include an athlete for women's sports? Surely there must be some rule". This is understandable but please realize that the transphobes who are pushing this aren't concerned at all with the specifics. They're not even interested in women's sports. They want to remove trans women from public life altogether. Not just sports but everywhere. Intimidating trans athletes into obscurity is just their most recent tactic.
So please remember that there is no test that will satisfy the transphobes. There is no fair rule that can be agreed upon, because the transphobes will always keep moving the goalposts. This gets extremely complex. There is no use in debating these people. They will debate forever, because the actual deep down motivation is disgust with trans people.
Save your energy. Don't debate transphobes.