JPA spec 4.6.1 defines

Enum literals support the use of Java enum literal syntax. The fully qualified enum class name must be specified.

so the new behavior is actually spec compliant. Allowing integer literals before 5.0.3 seems to me more like a bug than a feature.
Using a shortname in case of enums is not possible as far as I know, but you can use parameters instead if you are concerned about readability.