A33Zab;
What do they mean with -except level off is performed-?
level off as result of this speed protection or level off due to CRZ?
From memory!,... they would mean a level off performed by the pilot either in auto flight using the FCU or manual flight using the stick, (autothrust either engaged or not engaged).
As I understand and recall it, a "level-off" is a term that refers to a flight phase change from either the climb or descent phase to a leveling off (no change in altitude), even if the level-off is temporary. If the altitude at which the aircraft is leveled off has been entered in the MCDU PROG page under "CRZ", the FMGC enters the "ALT CRZ" mode for speed and power settings which use the CI and other information entered into the MCDU by the crew either at the start of the flight or during the manoeuvre. "ALT CRZ" is displayed on the PFDs.
If the level-off altitude is different than the altitude entered in the MCDU PROG page under CRZ, the FMGC enters the "ALT" mode and displays "ALT" on the PFD, indicating the difference between the MCDU setting and the captured altitude.
I suspect the meaning of the quoted passage is, the protections afforded in the listed modes don't apply/aren't available when the aircraft is leveled off...which makes sense. (It's interesting to note that ALT* is a protected mode).