If you create a Flow board at an unused location, Special:EnableFlow attributes it as you'd expect (the board is created by creating a description, that description is attributed to the real user).
However, if you create it where a page already exists:
1. The page is archived.
2. It is converted from the archived location to the Flow board (using the Converter infrastructure).
3. It is attributed to 'Flow talk page manager'.
It should be possible to attribute it to the real user. The only groups FTPM has are 'bot' (not really relevant, since this doesn't need to be marked as a bot edit) and 'flow-bot) (which by default only has 'flow-create-board'). To use Special:EnableFlow, you need to have 'flow-create-board' anyway, so it should work out.
This will require refactoring Converter somewhat.
People have been intentionally exploiting this in production, including on high-impact pages.