In the CFF.SAMPLE(CFTPARM) member we find disable the compression in the CFTPROT for SSL ?

CFTPROT     ID         =  %PROTSSL%,        
           NET        =  %NETTCP%,          
           RCOMP      =  0 ,              
           SCOMP      =  0 ,        

Does it mean the compression is useless when doing SSL transfers?

Using the online compression along with the online encrytion is very heavy in CPU consumption.
SSL itself slowdown a lot file transfer time (depends of the system and how is handle the cryptography)
Adding the online compression to an SSL transfer add even more CPU consumption and it ends in most case with an overall time to transfer the file higher than using SSL with the compression.
But again, because file compression is managed before the encryption, for very large text only files, it may worth to give it a try.