To be fair with Heinberg, I'm not sure if the concept of sliding timescale was firmly established back in 2004 when he wrote the first draft for Young Avengers. According to Marvel Fandom, the concept and its specific rules were only officially discussed in Marvel Handbooks published after the first Young Avengers volume, so it's possible he was just really clueless to how chronology worked due to a lack of clear rules and editorial wasn't of much help at the time.
And speaking of editorial... Tom Brevoort is leaving the Avengers office after many years being in charge of the franchise. As some of you may or may not know, he was one of the minds behind Young Avengers and edited most if not all books with YA in the title. While I'm super thankful for him helping bring the team to life, I'm also low-key bitter about the fact he left the team in limbo for so long after Gillen's run. Here's hoping whoever takes over the Avengers franchise will actually bring the team back into the spotlight.