Wow, that’s shitty. Because you could simply have taken the same time off under unlimited PTO as by burning down the accrual, the company effectively zeroed out accrued vacation time. I’d be pissed that happened to me.
I mean, in real terms, I've come out way ahead since I get a lot more PTO now and probably wouldn't have cashed much (if any) out when quitting regardless. If the alternate was to keep my measly PTO allowance but still get the possibility of cashing it out someday when I quit, I am definitely happier this way.