It's not just a matter of "you can" - it's "you should".
The important thing is have both a backup of the catalog in a consistent state and a backup. If you already have a full backup strategy for your machine (and associated drives) it does not matter if this backup folder that Lightroom saves the consistent backups to is on the same drive or not. But it is absolutely essential to distinguish between the two purposes of the "backup". Backup will easily get misunderstood.
In my opinion one should not have a separate backup strategy for the catalog "backups" that is different than for the rest of the system. Everything including catalogs, RAW and associated image files, documents, etc. should be backed up on several copies on different media and be in different physical locations.
