If memory serves, Postgres actually parses it to int128 internally.

To the best of my knowledge, a uuid's string representation is only that: a commonly accepted string representation that makes it easier to read. As much as the RFC suggests a format, you'll find everything and anything in the wild.

Back when I was still playing with TSQL, for instance, I vaguely recollect that GUIDs were formatted using caps with wrapping braces, e.g. `{A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11}`.

There also is a whole heap of legacy systems whose poor man's uuids were generated using `md5(something)`, yielding things like `a0eebc999c0b4ef8bb6d6bb9bd380a11`, and whose data begs to get converted automatically at some point or another.