Apparantly you can’t comprehend that a blockage that creates pressure would increase the volume of the reservoir in the sump since it’s not pumping as fast as it needs too. Or if it’s low, it could be pumping too fast because of a leak.

You’re almost there, you comprehend the basics, but fumble with the gauges being different information that a gauge. Your full sump can also overflow, but your pressure gauge can’t tell you that specifically either.

The gauge is only the sum total of all the parts, it tells you NOTHING other than to check the system, which you should already do regularly regardless anyways.