I don't think anyone is "railing against SEEN". We're in a dire situation in many workplaces, and a means for people to come together to try to reverse the policy capture and underlying false consensus in their institutions is certainly welcome and needed. But that's not to say there aren't good and relevant questions to ask about the end game.
I'm old enough to remember Stonewall being a force for much good in workplaces. I got into trouble many years ago for distributing one of their questionnaires in my then workplace (it was a questionnaire about workplace discrimination, it was the mid-90s and they were planning to campaign for a Sexual Orientation Discrimination Act). It would never have occurred to me then that Stonewall would become part of the establishment, a bullying organisation arguing against the rights of the very people they were set up to promote.
When my own workplace instituted an LGBT network (about 15 years ago) I thought it was a very good thing. Similarly, if you'd told me that network would become almost entirely a vehicle for promoting gender woo, represented on all relevant committees and claiming to speak for all "LGBT+" employees, listened to by management and a core part of my workplace's EDI strategy, I wouldn't have believed you.
I hope the SEEN groups flourish and do well. I hope they're the beginning of bringing sanity back to our captured institutions, and I'm full of admiration for the volunteers who are working so hard, in difficult circumstances and without resources, to set them up. But I don't think that should stop us asking the questions that Helen Joyce raises, about the end game. As I understand it, her piece is a talk she gave at a gathering of SEEN activists, organised and resourced by Sex Matters. It's about discussion and debate, not trying to undermine or stop anything.