Hm... thanks for sharing but this is very strange. My 1080ti hashes for 20-21 MH/s. I run the miner at 24 Intensity with overclocks of +300 memory and + 90 core (about 1770 MHz I think?) at 80% power.
I obviously don't know the overclock limits of a 2080ti but maybe the default intensity is bottle-necking you.
but x16r hashrate, can go up and down depending on combined difficulty of the block-algos..