No, UUIDv8 offers 122 bits for vendor specific or experimental use cases. If you fill those bits randomly, you get the same amount of randomness as a v4. The spec is explicit that it does not replace v4 for random data use case.
reply> To be clear, UUIDv8 is not a replacement for UUIDv4 (Section 5.4) where all 122 extra bits are filled with random data.
Yes, vendor-specific data can be 100% random.
replyIt can be, but you should prefer UUIDv4 if you do that. One problem is that UUIDv8 does not promise uniqueness.
reply> 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/