>>191796607>No matter how you look at it there are important details missing about what happened during the timeskip
Well yes, we have the whole year of the timeskip completely missing on top of having no access to either Eren nor Historia's POVs of this year and the previous ones, since all timeskip flashbacks so far were told from the perspective of other characters and only one of them (Hange) was focusing on Eren's attitude towards Historia.
Up until this chapter the last time we'd seen Eren and Historia interact the latter was on the verge of tears because he defended her. That in itself wasn't much to go off of but in light of the situation of both characters post timeskip (Historia preggo, Eren going nuclear and working with his brother of all people) educated guesses could've been and were made about EH possibly getting involved with each other in one way or another at some point after the Kiyomi meeting.
Chapter 120 confirmed that said involvement does exist and that it was emotional in nature, without necessarily clarifying its exact circumstances. As such, flashbacks or memories from Eren's and/or Historia's POV are to expected.