By default no, illegal usages of unallocated allocatable /disassociated pointers is not something compilers are required to catch and report and there would be some extra runtime cost to it in general. Not very high in the context of an assignment to a whole allocatable for this specific example, but I think this should fall under a more generic runtime check option for bad dereferences of ALLOCATABLE and/or POINTERs.
Runtime checks are not on the top of the list given there are still F2023 features + performance and OpenMP/OpenACC work, but you are more than welcome to work on it.
You will need some strategy to conditionally instrument the IR and add related runtime to detect and report bad usages. Ideally this instrumentation will be cheap and not prevent optimizations (e.g., it will be hoistable/deletable if the usages are removed and/or it can be proved at compile time that the code is valid).