Yes, this. The only (small) downside with the Costco/
Alamo bookings is that you have to make a phone call to cancel rather than just doing it online. However, the phone system is completely automated, so you never have to talk to anyone or wait on hold. Just respond to the voice prompts and you can complete the cancellation process. I do this routinely as prices drop between initial booking and travel. I’m hoping that still happens for a July trip we have booked, since the rental car is about 2X what we have usually paid for a week-long rental in prior years/trips.