The “time part” is actually two different parts: the required millisecond-level ordering and the optional use of part of rand_a (which postgres does) to provide higher-resolution (nanosecond, in the postgres case) time ordering when combined with the required portion.
So, no, the “time part” of the postgres implementation is, in part, one of the options discussed in the spec, not merely the “time part” required in the spec.
So, no, the “time part” of the postgres implementation is, in part, one of the options discussed in the spec, not merely the “time part” required in the spec.