The game is perfectly functional.
I don't know if there's any actual consequences of that non-implemented copy protection, but I know I have fully played through the game, and the only odd thing I found was the blood sometimes glitching and appearing yellowish instead of red.
To give further info on Haze's post: You're falling into exactly the same trap that arcade developers devised back in the day, and it's honestly pretty funny.
Assuming you were playing through the game in mainline MAME and not some super-secret version that has hacked around all of the protection checks rather than emulating the relevant protection device, the truth is something that I believe some arcade manufacturers pivoted off of when devising protection checks to guard against bootlegging: You're not that good of a player.
Historically, some of the most nefarious copy-protection checks have been those that only affect players after a significant amount of time, or those with a significant amount of skill. For the former, I can only direct you to this article that was authored surprisingly long ago, back in 2001: https://www.gamedeveloper.com/business/keeping-the-pirates-at-bay
For the latter, all I can point to is the sheer number of games where a lacking level of protection emulation has only been obvious in later levels of a game. Sega's "Quartet" had issues with its copy-protection hookup for quite a while until - and Haze will correct me if I'm wrong here - Haze noticed that some levels that were a good ways into the game ended up with moving platforms that the player would simply clip through.
At the time, within the scope of the arcade market, the best sort of copy protection was one that was inconsistent
. If you have a game that wedges itself at the first sign of trouble, you immediately give any bootleggers that are kitted out with an ICE (in-circuit emulator) for the relevant CPU a sequence of events that they can use to reverse-engineer the protection. If things are more subtle - some play-throughs work fine, some don't - then you end up with an altogether more sinister way of sowing chaos and distrust at the particular arcade that has bootlegged a particular board.
All of that is to say that we don't know what we don't know, but what we do
know is that the protection has not yet been fully defeated on Primal Rage. It could very well be that you've gotten through multiple play-throughs of the game. Well done, you have some remarkably good luck.
In the meantime, the people who have actually poured their hearts and souls into MAME, for anywhere from the past few years to the past quarter-century, have done enough homework to know that what MAME currently presents - and by extension, any hacked builds, whether they'll acknowledge it or not - is not an accurate representation of Primal Rage. That's why it's marked as not-working, and that's why debating over which set should be the parent set amounts to shuffling deck chairs on the Titanic until someone steps up to the plate and volunteers the time, effort, and skill with a logic analyzer to figure out what is actually going on.