Yes, it is ultimately TT. The order goes: UTC -> TAI -> TT

I could argue the TAI to TT is the second step. But let's put the pedantry aside: Is your best answer of something made easier in the modern world by leap seconds ensuring that solar noon happens at exactly 12:00:00 four times a year on an exact line of longitude for the time zone? And 4 times a year would require a time zone that does not honor daylight time, otherwise it is twice.

I'm not some crackpot here talking about the absurdity of leap seconds. US, China, Australia, Japan, S. Korea are on board for discussions about abolishing to happen in 2023.