The 5.2.11.Final codebase still contains //TODO: implement 2nd level caching?! natural id caching ?! proxies?! at EntityType.loadByUniqueKey

I think that the reason for premature loading is to check whether the relation is consistent. @LazyToOne dictates already whether it is even possible to postpone the check, but if proxies are in fact allowed then there is still @NotFound to be considered. When proxies are allowed, I'd leave this to a new NotFoundAction or the fact that @NotFound is not declared dictating that referential integrity is enforced thus the load could be be postponed by returning an uninitialized proxy.

PS. What still is left is that what should happen when value belongs to LazyGroup or instead of lazy it is actually eager but these are another problem stated at HHH-3930 Open
PS. What comes to being enhanced or not, I believe HHH-11147 Open has to be resolved first.