we had an extensive discussion thread on this a year or two ago but I don't think that was a conclusion..

Most corporate reservations include the language about changes triggering reprise or possible extra fees etc .. I had my legit corporate reservations change price online a couple times which was not due to corporate rate change - in both cases hertz had correct rate in the system at pickup.
Given how dysfunctional hertz is these days I suspect some IT glitches rather than changes to corporate rates.