My guess would be that the PO lost the key & the original locks were replaced with whatever they could find that would fit.
My experience with Isuzu studs, is that the earlier (1st gen Trooper) ones were more prone to stripping than the ones on the VX.
I only ever use a socket & ratchet (no air tools) to change mine, no problems so far & I've probably had my wheels on & off at least twenty times in the last 4 1/2 years.
I know it's overkill, but I have three McGards in each wheel...
My theory is that maybe it'll slow the thievin' bastiges down enough for me to catch them doing it...