Oh, I don't say that one forgets absolutely everything. But after an interruption of twenty years, there will almost certainly be so many missing elements -- "holes" in one's game, so to speak -- in everything from muscle memory to recall of cockpit procedures that once were automatic that the benefit of the 27 hours is likely to be quite small. Who among us, if we were out of the game for so long a time, would then consider themselves capable of performing the following on a consistent basis without additional training:-
1. Emergency procedures.
2. Crosswind landings.
3. Operations in congested airspace or at busy airports.
4. Cross-country navigation, with and without navaids.
5. Unusual attitude recovery/slow flight/steep turns.
6. Soft and short-field take-offs and landings; flapless landings.
No doubt I'm forgetting a few things. But take care of getting the candidate up to speed on those items, and that's a lot of the 27 hours duplicated right there.