I honestly think he was able to see something with his sharingan eyes because sharingan can perceive shifts in chakra so he might of seen some weird movement of chakra but couldn't tell exactly what's going on. In same time boruto perceived time was frozen but sasuke noticed something so maybe that whole conversation was going on in his head.Yea SB.. It's a no-brainer on that bit!.. Thing is, we don't know what he seen exactly or heard but I'm sure he got the just of it an is not satisfied by his discovery..
To be honest Bee.. I can't stand this month to month jive when new content is being released....
I feel you bro hopefully they move to weekly releases. But seems they got planned something since next chapter is released April 4th and the anime starts April 5th.