I understand what you are saying and if it was for my own book, self published, I would agree (as I am doing these things).
However, coming from a publisher I have to say that this looks more and more like a red-flag to me. The whole point of being an author is to write books - not to be a marketing agent for books. In self-publishing this is a necessary evil which comes with the territory.
Basically it comes down to this: If having a pre-existing social media profile and activity history are requirements for success in this call for submissions, then this publisher is treating this process in the similar vein to a vanity publisher. How are we to know that they are not selecting the authors with the most twitter followers as their primary selection criteria?
With a ready-made audience and a free marketing employee (the author), the risk to them is decreased and the legitimacy of the submissions process is compromised.
I know that they are a legit publisher but this element feels shady to me. I would like to know what Victoria Strauss and co think about it tbh.
It's not a requirement. It's a bonus. As I've said before, when I submitted, I had no public persona. After I learned more about the industry and saw how pretty much every author has a Twitter and a blog, I made them. There are some Angry Robot/SC authors who aren't as active on social media. They were still signed.
Writing is not a vacuum, and it hasn't been for a long time. Marketing and self-promo is a large part of the writing job, whether you're published by Pan Macmillan or put your book up on Kindle yourself. It's not even remotely a red flag. What about going to events? BEA is coming up, and lots of authors are going there, flown by their publishers, to promote the heck out of themselves.
Calling SC or any publisher a vanity publisher because they want their authors to help promote their product is rather rich. I've been edited multiple times, they commissioned original artwork, my books are on the shelves in Hawaii to Canada to Heathrow Airport. A friend sent me a photo of my book in New Zealand.
My own self-promo and blog tour helped get the word out, but Strange Chemistry still do way more for me than I'd ever know how and I'm grateful for that.
Even you posting on here is social media, and to be honest, basically insulting the publisher you're planning on submitting to when the commissioning editor has posted on the thread seems rather foolhardy to me.