If the transfers are using DEST members like XCOM1 and XCOM2 as such, it correctly use COMPRESS=YES in the absence of a different COMPRESS setting in either the DEST member or the SYSIN01.
Even a TYPE=SCHEDULE transfer to a specific LU will use a DEST member, IF the LU name is defined in a DEST member that is ENABLED in the XCOM server at the time the transfer runs.
If the transfer was submitted to an LU for which there was an enabled DEST member (XCOM1 and XCOM2). This would have caused COMPRESS=YES to be used - UNLESS COMPRESS=NO was specified in that particular DEST member being used.
In NO case will COMPRESS_ALLOWED be overridden by a COMPRESS parameter or default.
So, if you wish to completely disable or limit compression use, COMPRESS_ALLOWED will overrule any COMPRESS parameter setting that is used. The default setting for COMPRESS_ALLOWED is ALL. If you want to completely prevent compression from being used, you can also do so via the COMPRESS_ALLOWED parameter in the CONFIG member.