The so called "blanc day" is a relict from the old FTL. The new FTL, in place since almost a year now, allows, however, exactly the same procedure if hotac standby is scheduled. The definition for hotac standby can be used also as home standby.
Only in the case of airport standby is a time frame for standby required.
Is there any airline in Morocco which is not using the "blanc day" procedure?
This problem of interpreting the FTL is not only a Jet4you problem, it is certainly a DAC induced situation as the intro of the new FTL in November last year has not been done in a proper way. There is no explanation nor guideline published. And since the union is busy with the nationalization issue, the airlines introduce more and more unwritten rules on how to read and understand the FTL.
21 hrs duty, are scheduled, 29 hrs duty are not rare, resetting the 7-day limits to 0 hrs after the 36 hr rest period, 1 hr check-in timings also, certainly for most airlines with base Casablanca, 1.5 or 2 hrs are more realistic etc.....
And in the case of Jet4you, don't forget that politics, schedules and other important issues are solely set and determined in Zaventem.