In our "Using the OS/2 Backup/Archive Client" book, under ERRORLOGRETENTION:

"The error log is pruned when the first error is written to the error log
after an ADSM session is started. If the only ADSM session you run is
the schedule, and you run it 24 hours a day, the error log might not
be pruned according to your expectations.  You must stop the session and
restart it to allow the log to be pruned when the next error is written."

The error log is pruned, but not as often as the schedule log in some cases.
I believe this design decision may have been due to performance concerns.

MJ Lopatin
ADSM Client Development