Yes. Lightroom’s catalog backup is more than a simple file copy. Based on the community answers, it typically includes an integrity check on the catalog, copies the catalog, may optimize the working catalog for performance, and stores the backup as a zipped file to save space. That extra work explains why it takes longer than manually copying the .lrcat file.

A manual copy can still be useful, but only if Lightroom is fully closed. The catalog is an SQLite database, so copying it while Lightroom has it open is not considered safe.

If your regular backup system keeps multiple versions and runs consistently, it overlaps with Lightroom’s backup quite a bit. The main advantage of Lightroom’s own backup is having point-in-time catalog copies that can help if the catalog becomes corrupted or if you need to recover from user error. In short: your external backups may be sufficient if they are versioned and reliable, but Lightroom’s built-in backup adds a convenient extra layer of protection.