It can be, but you should prefer UUIDv4 if you do that. One problem is that UUIDv8 does not promise uniqueness.

> UUIDv8's uniqueness will be implementation specific and MUST NOT be assumed.

Here's a spec compliant UUIDv8 implementation I made that doesn't produce unique IDs: https://github.com/robalexdev/uuidv8-xkcd-221

So, given a spec-compliant UUIDv4 you can assume it is unique, but you'd need out-of-band information to make the same assumption about a UUIDv8.

I wrote much more in a blog post: https://alexsci.com/blog/uuid-oops/