Well thats news to me. Ive done it probably 50 or 60 times now between ANC and FAI

You check in for one and it gives you the option to select "checkin for return flight"
Well your one is news to me (and I may humbly admit my error if that's the case), I've not done 50 or 60 but every time I have a RT I can never get to the OLCI options for the return until after the first leg is flown (yes, even when they're both with 24 hours). The most important part of OLCI for me is the option to adjust flight times - can you do that for the 2nd leg as well in this magical "dual OLCI"?