[roundabout-host]

It is possible for e-signatures and similar variants. However, there is no sign that the "age verification" will support this variant. If you go to the demo <https://cinema.ageverification.dev>, no option is given other than the Android/iOS app.

So it seems that the app is only an alternative in the case of government portals, but it is not an alternative for "age verification".

[lern_too_spel]

The German implementation already allows it. The GitHub issue you linked to explains multiple times that it is a reference implementation, as have several previous HN comment threads linking to this page. It is not the actual implementation that any country plans to use.

[roundabout-host]

The German implementation allows it for some uses, but not for "age verification". The demo does not account for the fact that other options may exist.