Comment by ralferoo

Yeah, in practice the 6 bits you lose aren't important. Redoing his calculations with 122 bits and a quadrillion generated IDs (that's a million billion), the probability of a collision is 9.4 x 10^-8 (or one in 10 million) using UUID v4.

In my opinion, UUID v7 is useful because you per millisecond, you still have 74 bits split between user defined (up to 12) or randomness (minimum 62). If you choose the minimum 64 bits randomness, you can read the numbers straight from the article - 1 million UUIDs per millisecond with less than one in a million chance of collision, but you still have 10 bits to add additional data, such as which machine generated it.

If you stick with just time and have the full 74 bits of randomness, you can generate a trillion (10^12) UUIDs per millisecond with less than one in 40 billion chance of collision (2.6 x 10^-11) using UUID v7.

I think the fact the formula is (k^2/2N) actually shows that having a time component makes better use of the bits than a purely randomised space. In this example, we have a lower chance of collision with a trillion (10^12) UUIDs generated per millisecond than a quadrillion (10^15) UUIDs across all time.