Yeah, I’d have passed as well.
It’s definitely an inexact science for that version of the game, especially for combos. Kind of a “know it when I see it,” and even “know” is a little strong, as there’s always going to be some guesswork.
That grand looks to be too far away to factor in enough for a true combo. The best I can say is I’d want that grand at least a bit above the major in that example.
If you see any other close plays, post them here.