That scenario is a risk even if it is in the same booking reference - there is nothing to say you don't have another flight departing with another airline even if they are booked together. In my case the flight was the next day (one night stay) so unlikely in my case.

The OLCI has redundancy in place to cope with this, you cannot board an international flight with OLCI only and not an actual scan of your passport. The onward ticket requirement could also be flagged and asked for evidence of at the Gate.