Du kannst an 2 Reisetage mit beliebig viele Züge im Heimatland fahren und auch dein Heimatland durchreisen. 

das heißt ich kann auch einfach zwei inbound-reisen machen, mit dem mobile pass? weil es sowieso nur die kategorie “im heimatland reisen” zählt ? (de facto will ich nämlich zwei inbound-reisen machen und gar keine outbound-reise)

Der mobile Pass macht gar keinen Unterschied zwischen Ein- und Ausreise. Also: ja, das geht.

I found the easiest way to consider the 2 In/Out days is keep it simple. 

On up to 2 travel days of your allowance you can treat your own country in exactly the same way as all other countries in the scheme. (Global Passes only)

A travel day is one where you can join any train in the scope of the pass scheduled to start between the hours of 0000 CET to 2359 CET. You do not need an extra travel day if the final journey ends after 2359 unless you  take a further train on the “second” day.

Although they are called in and out days you can use these 2 days in any direction and do not even need to cross a border. So you could use a travel day to travel from home to a ferry or airport. You can go in any way and break your journey as you wish.

With mobile passes, these 2 days are managed by the app, and when you try to add a trip that will use one of these days it will prompt you for confirmation.

I have just completed 2 breaks with a 2 month 10 day Global Pass, flew out of the UK for both, then used my 2 days for Eurostar and UK trains back to home.