Yes. And this makes any kind of data analysis a lot harder.
On paper I work the same number of hours as my Japanese coworkers. In reality they work more than double.
It's the same way on-call for many companies is just rolled into salary.
I've managed projects as a senior dev while the senior dev sitting next to me was purely technical. Etc etc.
The truth is two senior devs sitting right next to each other can have wildly different actual job duties.
I suspect glassdoor has taken at least some of those differences in work duties vs stated title into account.
> because it wouldn't vary the immediate effect on apples-to-apples salary,
Why wouldn't it?
Its not uncommon to stay at a certain level/title for 3-5 years.
You can't just ignore hours worked because "salary".
I come from a strong union background where you would get overtime or be able to take the time off later and where there were fairly rigid job duties. Where interviews and scoring candidates is all done in a very standardised fashion.
And oddly enough after adjusting for these explicit factors we had a very small unexplained gender pay gap. Much smaller than average for the tech industry.
Perhaps it's in our interest to make these factors explicit rather than implicit?