The documentation of QAnimationDriver::advanceAnimation currently claims:
"Since 5.4, the timeStep argument is ignored and elapsed() will be
used instead in combination with the internal time offsets of the
That sentence was added by Gunnar before 5,4 in dfc8f8b5d4a02f33c7f9063c2a28450902a9d863, and that time QUnifiedTimer::updateAnimationTimers(qint64) did indeed ignore the currentTick argument.
In 5.9.4, with commit 0c9e379dd8c57fab9d8e6ba8d35a0dca8ac05a0a by Jan Arve, this was changed and updateAnimationTimers() does uses the currentTick argument. This makes the documentation wrong.
There's a related comment "// ### Qt6: Remove timestep argument" on the QAnimationDriver::advanceAnimation() declaration, which appears to be outdated too.
I have actually no clue about the class and how it should work, but this appears to me to be a clear difference between what the documentation claims and what the actual code does.