I'd also like to add that I've been told syntax-propertize is a property of font-lock and relying on it for correct operation on syntax-tables is ... not entirely guaranteed.
Basically, if a user disables font-lock for whatever reason (maybe scripted automation?), you can no longer rely on the syntax-properties to be correct.
It might be a bigger problem in theory than in practice, but again it represents yet another inaccuracy in the syntax-model and analysis of it.
It would be nice to get this stuff cleaned up.