First: thx for taking the time answering.
I do actually make use of the true/false state shown on the map. Currently, by looking at the map I manually take down a specific marker which I put into the PCN field of the cache such that I can later run queries based on that marker.
The situation for many of us is that we go on a hike and when we hit challenge caches where we don't meet the conditions, we put a "Write Note" log in and later, once we meet the conditions, we either log a new found-it or convert the earlier write note into a found it. That is best practices and complies with the GC's guidelines.
Now here comes the point: in order to do so, we need to re-run the checkers in order to figure out when we actually have met the conditions. Therefore the API as we certainly don't want to manually do the thing on the map.
If procject-gc implemented the method you pointed out at the bottom of your answer, running the checker (periodically?) on a VGPS, then I would put all challenges in question into that VGPS, export it as a GPX and process the result in whatever tooling is appropriate, e.g. GSAK, In this case I'd need the true/false somewhere in the GPX otherwise it isn't of much use really. I'd assume the true / false could be placed somewhere into one of the "User" fields that are already there, assuming they make it into the GPX then. Of course there would be other means to put it into the GPX, feel free to come up with our own ideas, whatever fits into development.
Thx again for your answer