That's not remotely universal, but they did consider that. It's immaterial.

It's really not immaterial. Power users are also the ones that get anyone to install Firefox in the first place.

Considering Firefox market share trends all decisions at Mozilla should be by default considered textbook material for what not to do.

The power users I know do that immediately and then it becomes uncertain. Also, most of these metrics suck. We didn't always collect such metrics and I wouldn't say it did improve software in general. On the contrary, it probably brought in far more dark patterns than better UI.

To hell with it and then some. Also to ignore uncertainty means you will be wrong. There is no "perhaps" or "likely" here.