Those files do not contain valid Simulink .mdl . Simulink .mdl files are text files, and they start with word 'Model'. Those files are binary files with no discernable structure.
My test software says that the files are not compressed with any utility that I was able to find "magic numbers" for.
The files are not .slx files renamed.
It is possible that the files are encrypted using some utility or other. They are, however, not Simulink Protected Models.
