mm..i don't really know anything..but that definitely would make the scene all the more meaningful..after all many of their happy moments were rudely interrupted (although unbeknownst to them)..
i don't believe this was how it was in the book, though. that said, if it had occurred as you suggest, having it all end so soon after that perfect moment would definitely make the scene where jack remembers this all the more devastating. if anything, the dozy embrace had to have occurred sometime at the end of the summer because ennis probably needed some time to build up to that level of comfort..