Of course it should be disallowed, players who have samp addon sometimes are not getting killed by saw, so it should be considered as health hacking for sure.
I don't know if getting saw skin hit back would fix this issue or not even that I'am sure you are not getting it back in all cases. So either you bring saw skin hit back (if it will fix the issue of course) or disallow the samp addon that gives advantages to players using it over the others who are not using, on the other hand, we all can not just install samp addon and play because some weapons will be useless like saw and sometimes nades too, and it also gets the passengers getting damage instead of the driver who is supposed to be getting the damage.
For clarification: Watch this video:
https://www.youtube.com/watch?v=ufNKLt5w6BI (Fag quality)
As you can see in the video, Wolf didn't get damage at all even when Smoken the one who got sawed with him died as he wasn't using samp addon. and at the second part of the video he should have died when I sawed him after I shoot his wheels but he didn't get damage again and I got killed at end.
When I asked him how it that possible. he said,
Remove it please, this is a real mess.