Zel is confusing the store transaction logs (\EXCHSRVR\MDBDATA by default) with the IMS connection logs (EXCHSRVR\IMCDATA\LOGS by default). Store transaction logs are purged by the online Exchange-aware backups, but this doesn't touch the IMS connection logs at all.
You can happily delete the \IMCDATA\LOGS, and also check the \IMCDATA\IN\ARCHIVE and \IMCDATA\OUT\ARCHIVE directories whilst you're at it. These directories are written to if you set the IMS logging - check the IMS's Diagnostics Logging tab for the options to turn on or off the various logging - the ARCHIVE directories are written to if you have Message Archiving turned on, which is the default I think.
Remember you have to stop and restart the IMS service after you make changes to the logging tab so that your changes take effect.