My guess would be that the DTV is making it very difficult for them to use the "you stay in thailand too much" excuse, since it its multiple entry and exactly what they ask for when they give you a hard time on tourist visas (a proper long stay visa).
Another issue they face is the classic "lack of funds" reason for denied entry - considering you need a hefty amount of money to even get the DTV. They also dont have the time to go through all the supporting documents at the booth, while hundreds of people are waiting in line.
However, I am almost certain that the soft power variants of the DTV will be looked at more thoroughly in the inspection zones nearby, probably in the near future. And maybe the workcation category aswell (however that one requires you to have income too, on top of the 500k THB).
But if your documents are in order, you still have the amount required for the DTV, and you fulfill the requirements for the visa - I would not expect issues even at secondary inspection. I have seen reports online of people doing the extensions at immigration aswell, but there they seem to require even MORE evidence, and company stamps (who even uses those anymore?), etc. So good luck with that.