Democratic leadership are more comfortable running anti-abortion Democrats in hostile territory than they are running pro-single-payer Democrats in safe states. Feinstein's comments are typical.
So they tolerate the occasional Democrat who isn't 100% in-step with NARAL on a few races per year they probably won't win anyway. If it were a question of being 1/10th as strong as single-payer supporters are right now among viable candidates, the party leadership would be freaking out about upsetting their donor base.
And how many Democrats have anything more than a symbolic interest in single-payer?
I don't know what politicians having a "more than symbolic interest" would mean.
I'm confused here: are you upset about the Democrats not sufficiently supporting single-payer, even though you aren't totally convinced it's the way to go? Or are you just upset that there are Democrats who oppose abortion?