For caves in Mexico, if you are relying on the permanent line arrows for navigation, then you have already made too many mistakes. What do you want the arrow to point to: (1) the nearest exit 1,000' away through a small silty tannic siphon that opens to a cenote that is impossible/ difficult to exit, (2) the exit 2,000' away in large rock floor passageway where you can easily swim three abreast. Are you diving on DPVs or swimming in sidemount, etc. Add to this that often sections of cave were explored by different teams from different cenotes and were marked accordingly. Once you are beyond the easy tourist distances, it is rare for anyone to go back and reconcile the arrows to the "fully explored" system. As an added bonus, there are people that still go in and screw around with permanent markers. You solve these issues on the surface by reviewing the map and having a good plan with contingencies based on the exits you know. A dive that ever results in trusting the direction of permanent or temporary arrows you didn't install (or confirm with your own non directional marker) was a failure before the team splashed.
You are right Mexico has its unique system of navigation markers that can be less than reliable. I remember one line arrow pointing as an exit on a side line, and was told later it lead to a choked out sink hole. Also, line arrows have their political past, and have been the subject of the famous "line arrow wars" about 15+ years ago. Sometimes I wonder, and perhaps wrong,but there doesn't seem to be a lot of incentive to make navigation in systems simpler because then it would reduce the dependency on guides.