I thought the cut away to the flashback was superbly executed; perhaps Lee could have used a fade to show time movement backward, but I think that would have been too literal. The thrill of realizing the flashback quickly, and the "I got it" rush was wonderful...and very, very foreshadowing. Had the flashback been less subtle, the clouds of ominous things to come would have been too obvious, imo.
Also, the dozy embrace itself, was, to me, sensationally uplifiting, joyous, moving, emotional, and truly male. The manner in which low-key Ennis dominates the embrace and hums to Jack is one of the most endearing 'love scenes' on film. I rate it up there with the end kiss between Audrey Hepburn and George Peppard in Breakfast at Tiffany's. The richness of their singular being is clear. pure wonder.