> the 10-15 seconds I mentioned is the daily variation in solar noon.

Yes, but averaged over an entire year, it still comes out to zero. The difference between mean solar and atomic time does not. It accumulates over the years.

> we just reversed that decision

We paused it for 100 years after 2035. That doesn't change the physical fact that the Earth's rotation will continue to slow over the long term. We might eventually decide to just not care about that when it comes to civil timekeeping, but that's not what the decision you're referring to did. It just said we can afford to let the difference between UTC and TAI accumulate from 2035 to 2135 (by which time it is predicted to be about a minute) while we figure out what we want to do over the longer term.