This appears to be because the Reaper collects referenced class names by using the first Identifier in the ObjectType non-terminal, but it doesn't recurse, so it misses any annotation type references and the type arguments (parameters).
I suspect the static import of a field not being classified as referenced probably is because the reference is to the field without the class being specified, so the import is removed because the class is unreferenced (even though the field in the import is). But I haven't confirmed this conjecture.