I can't really agree with that. The Future Champions demonstrably come from a time that's post-BotW. Sidon reflects on it being nice to fight alongside Link again, and Yunobo talks about how the Link from his time inspired him to be braver in the DLC story. There's plenty of tie-in, just the...
Nah, I wouldn't call it that disconnected. Sure, the events of AoC fall on a separate timeline, but it can't first exist without the events of BotW to set it up. It is a game that is clearly heavily intended to be experienced with full knowledge of the events of BotW for the best appreciation of...