On most fleets. Some are still brake. (The DC-9 for sure)

UAL contracts are billed by the minute. Not block or better. No "...or the greater of". Just pure block. OUT to IN. This is why UAL is power hungry with the EBR issue. They even feel like they're making a concession letting you use Lektro carts because they had to concede a minute to let you drag up and be ready to push. That puts them out to the tune of hundreds of thousands a year.

For what it's worth UAL's demand for D-0 is the secondary issue here. Just go when you're ready. UAL flights are so padded in the schedule anyway that the likelihood of making anything extra by popping the brake is remote unless you're grossly misrepresenting your times.

In which case the DOT and FAA might have something to say to you besides UAL and your CP.