Looks like the difference is that v4 UUIDs are random and v5 are SHA-1 hashes of names. **Reliable!!**<sup>[citation needed]</sup> source: http://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29
That means that what you are doing in this method is not a UUIDv5, but rather a reduction of randomisation of at v4 UUID<sup>[citation needed]</sup>

Someone should test if the plain random UUID works, too. (I can't, no time ._.)