Put 55 PSI in the tires then check the display in the truck. If it only reads 50 then maybe the tire monkey was correct. If it reads whatever you choose to run then forget the tire monkey. But kindly report results here.
2008 F-250 tires run default 65 PSI with in-tire TPMS. Guessing 2018 F-250 uses same TPMS as the F-150. I'll leave verification as an exercise for the reader.
Autel MX clonable retrofit TPMS is speced to 116 PSI. The Autel sensors support most all TPMS protocols so this only says the protocol Ford uses might report pressures up to 116 PSI.