That consistency is built on assumptions about the filesystem that may not hold true of a copy made concurrently by a backup tool.

e.g. The database might append to write-ahead logs in a different order than the order in which the backup tool reads them.

That's why you do a filesystem snapshot before the backup, something supported by all systems. The snapshot is constant to the backup tool, and read order or subsequent writes don't matter.

The main difference is that Windows and MacOS have a mechanism that communicates with applications that a snapshot is about to be taken, allowing the applications (such as databases) to build a more "consistent" version of their files.

In theory, of course, database files should always be in a logically consistent state (what if power goes out?).

> something supported by all systems

Well, supported by Windows and MacOS. Linux only if you happen to use zfs or btrfs, and also only if the backup tool you use happens to rely on those snapshots.

I believe basically any filesystem will work if you have it on LVM. Bonus of lv snaps being thin snapshots too