A lot of bikes these days have kinked seat tubes, meaning that the seat angle varies with height. I read somewhere that it is convention to measure the effective seat angle at the stack height, which would at least make it possible to calculate the seat angle at your ride height if you were so inclined. But is this convention universally observed, or do different manufacturers measure it differently, making it just another silly useless number 🤕
Normally there is an accompanying drawing and all the ones I have seen display the angle you describe.
I don't see how you could correct for ride height unless you also knew the actual angle of the tube bit the seatpost sticks in.
The taller you are the more useless it is! At 6'4" the most annoying thing about my Fuel EX