I've used all the tools: MTS, Crawl, turn assist, center, front and rear diffs. They all have their place.
One example was two weekends ago, wheeling offroad in snow/ice on a steep off camber downhill. Crawl control worked pretty well for this. Could I have done it without, yup, but since I had it, I figured I'd use it. It helped reduce the pucker factor.
But I think I misread your question. I haven't mixed and matched crawl control and lockers. I usually turn crawl control off unless I explicitly want it. I haven't noticed MTS activating when I was locked (not saying it can't happen, I just haven't seen that).
Also, I don't often lock my front axle, but lock my rear more frequently. In this situation, I'd think there is the possibility to have wheels turning at different speeds and trigger MTS.
Side note: I turn off VSC and RSCA any time I'm offroad.