I think time compression is not forbidden, it is only not advised. Perhaps I do not know clearly the rulebook, but I used to fly with x4 speed over the Ocean (only offline !!!) with ProPilot and I have never been penalized for that. It is crazyness to use compression during climb or descend because anything can happen that you need to react immedately, but it is possible to use on cruise... correct me if I was wrong. 
Advise (it seems like) or not, it is not a problem of words here, the statement is this from 4.6 Regulations:
'*4.6 Regulations*
....
It’s permitted to fly _at a simulation rate of 2x, 4x… as you have to submit your PC time_. For
example, if you’ve flown an 8-hour London – New York flight with 4x time compression in 2
hours, please report only those 2 hours!
/We’d like to know how much time you actually spend
flying for EuroHarmony
/. Note that if you fly online (VATSIM, IVAO), it is not possible to use
time compression.
...
You are not allowed to save a flight and continue it later as flights have to be reported only
via one pirep. _
If you don’t have time for longer flights, use time compression,_ or fly shorter
ones...
'
Well,
Robert, I do not think that using any feature of sim. at any time is crazyness or wise-ness. If the conditions are sufficient they could be used in any need. It is not permitted in online since the reference frame should coincide for all users at every instant. Besides that the speed of time applied during the flights is a relative quantity, one could be slow for me for a reason and that is crazy for you (Let me tell if pilot should leave the flight in say ten min. in the middle of a 5 hours flight, time compression would work well even at the decent). Actually, I conclude this feature as a calculation error of flightlogger which should be repaired.