It doesn't need to be mentioned when
they know it because that's what it is. Josy's words are literally a reference to it since we know for a fact that the ultimatum stopped them seeing each other all summer,
"Relationships when you can't be with each other every week suck", which this moment feels similar to because it again happens because of the threat of Patrick. Josy saying "before summer" is therefore meaning that this all started
before the summer break. We also know that Patrick was abusing Maya at the time of her graduation from high school because of her holding her arm in the picture which means Patrick had found out by then which was before summer. Therefore, he gave the ultimatum
before summer.
You really need to read my words more carefully. I said Patrick was the
catalyst, as in his ultimatum forcing this separation
exposed their communication issues which are the heart of the problem. It seems you want to paint their relationship as something that was always bad and you want to imagine they had problems, arguments, negative thoughts, etc, before Patrick forced them apart, but if you want to talk about things not being mentioned, well
this has never been mentioned.
What we know, factually, is that such things didn't happen until Patrick's ultimatum because it's never mentioned that things were bad before it. What we do get though, is Maya saying this:
"All those nasty thoughts I didn't want to have when Dad posed his ultimatum almost disappeared when the three of us got together." So this seems to say that it wasn't until Patrick's ultimatum that negative thoughts and feelings started to creep in and that will have started the rift.
But as I said in response to
Moni23,
"these are issues all relationships face, especially when physical distance is involved, and Patrick's ultimatum essentially exposed the holes in the ship, as it were, the things that all couples must face, the adversities they must overcome and not let bring them down if they want to make it work". Before the ultimatum, they didn't deal with any extreme adversity beyond simply keeping it a secret. Patrick driving the wedge between them exposed them to the first real challenge in their relationship and it almost broke them. It exposed a general weakness that such a hardship could almost bring them down because they had a hard time handling and navigating it. Good, solid relationships, which it would seem they thought they had, don't let such things ruin them, so this whole ordeal exposed them to issues they didn't realise were there and that they need to fix if they want a long lasting relationship.
TL;DR - Patrick's ultimatum exposed a weakness in the relationship, one they were naive to at the time, and it has forced them to confront and realise there are issues that need fixing by having gone through that hardship.