Number String or Int not allowed in Enum

When defining an enum with a Number String like `"11201"` or an Int like`11201`, it will result in a schema validation error `Names must match /^[_a-zA-Z][_a-zA-Z0-9]*$/ but "11201" does not.`

Why are number strings or Int not allowed to be an enum? Thank you!

snippet:
```
enum IsoClass {
11201
11202
11203
}
```

- assignee(s): @acao
- source:

---
_Note: Action Item issues are reviewed and closed during Working Group
meetings._