The mere fact that an XT-IDE interface is installed in the computer has in the past been found to prevent some games from working even if they are running off a floppy disk.
Edit:
Another reason why Bruce Lee might fail is that Datasoft copy-protected its disks with a weak bits protection scheme that may fail to detect the disk if the random data in the protected sector is not "random enough" by the game's standards. I am not entirely sure what determines the amount of entropy in a weak-bits-protected sector, but I suspect it is related to the floppy drive electronics and the computer's power supply. I have had this issue with an original disk of "Ghosts'n Goblins", which worked in a Tandy 1000 TX but not a 486 PC with an 1.2 MiB floppy drive, and debugging showed that the keydisk checking routine found the weak bits sector not random enough in the latter system.