Unable to use hyphen ( ' - ' ) in widget xml

So I came to the conclusion that you're unable to use a hyphen symbol in an enumerationValue key in a widget.xml file.

<enumerationValue key="enumeration-key">Key</enumerationValue>

is invalid for example.

I posted an issue at the Github repo of the AppstoreWidgetBoilerplate and Jelte responded with the fact that it is indeed not possible.

However it left me wondering (and Roeland aswell) what the reason is for this. If anyone of you have some more information to why this might be, I'd love to know!

Thanks!