&WRITE is used to generate a message from a NCL procedure. With LOG=YES parm, it is possible to send the message to the log from any environment except from the LOGP.
For this reason, &WRITE LOG=YES will not send any message if it is executed from a logproc exit running in LOGP.
The workaround consists of submitting another NCL procedure to a background environment from there.
Instead of &WRITE LOG=YES in the logproc exit, use the following statement:
&INTCMD SUB BSYS -EXEC ncl_proc
ncl_proc includes &WRITE LOG=YES