That is true at NERC (LATCC server). Elsewhere, there are much better trackers and filter systems.
STCA, as I remember is crap in London (unless it's significantly changed recently?). Constant false alerts. Poor track predictability (making vector leaders worse than useless).
There is a common ironic phrase we have :" STCA is not a control tool".
The truth is, we use it as such all the time. It works EXTREMELY well. And with on-screen cleared flight levels acting as STCA search filters, you can of course simply remove the CFL to "what-if" the effect of a continued climb/descent. No STCA: ok, off you go. If you do get one, it tells you the predicted distance down to .1 mile ish, and you can give an appropriate heading and continue climb/descent in one. Good bit of kit.
Another tool we use which is track-prediction dependent is VERA (Verification (of separation) And Resolution Advisory). Although not as accurate (of course.. you could be dealing with predictions at 10 min range), it still gives you a very good idea of when you need to give it a bit of radar handling, or when you can just lock a/c on current hdgs and look away.
Knowing what you're dealing with, it still amazes me that you push as much traffic as you do. But, with a little investment, I think simple tools would help you a great deal.
As you say, what does SMF do at the time? Buggar all.
Once again, wrong priorities!