Accrual PTO to Grant Basis?

In December, my company had a mandatory call in which they advised us that as of Jan 1, 2021, our PTO would no longer be on an accrual basis and would now be on a Grant Basis, which means that as of 1/1/21 we would be allocated our PTO time. However, when I asked whether our PTO balance would be cashed out or rolled over, HR responded that our balance would be rolled over, but our balance would only be cashed out if it was our final check. However, in that case, they would only give us the balance of our allotted time in 2021. She gave the following example as an explanation of this new policy:

If an employee normally gets 80 hours PTO, took 40 throughout 2020, and now has a balance of 40 hrs, then 40 hours would roll over to 2021. However, they would only give us 40 towards the allocated 80 hr PTO for 2021 (not independently of the 80 hours for 2021), because it will be capped at 80 hours. (Company should paid out what ever is over capped)

My question is: Is this legal, given that California it is not a use it or lose it state? Because in this case, we would all essentially lose either way on our accrued or on the PTO that should be allocated for 2021. This is especially destructive, given that we all have a larger balance of hours than usual due to Covid travel restrictions/cancellations. I’m quite frustrated with this decision, as they have now given us a mere 3 weeks notice to take our PTO. At this point, it isn’t even possible to approve or take the PTO time as managers–we have minimal coverage in our offices due to an unfortunate surge in covid cases (and an influx additional work to track, record and comply with all CalOsha reporting for these cases as a result)