Yes, indeed, you can express Q as U'DJ', that's legit. I can't see any way
you can count (FQ)^4 as more than 24 quarter turns, for thats all it is.
In the eyes of the people who count turns, not quarter turns, the
QQ in the middle (4 quarter turns) can be expressed as U^2D^2,
where U^2 and D^2 each count as one, which could be thus contributory
to counting the formula as 22 turns, but surely no more than 24 by
any kind of metric.
By the way, my description of the left-handed wrench in the
annotations was in error, it should have been (F'Q)^4, not (FQ')^4.
(The formula (FQ)^4(QF)^4 is correct as stands).