I'll add to the pile that this looks like TACC might have been on but not lanekeeping.
I've been playing with TACC vs Lanekeeping+TACC (I'm deliberately splitting these out to avoid confusion between stuff like "Autopilot" which means very little to most). TACC only has situational awareness to what is more or less directly in front of you. So if you're turning around a bend, for example, it won't slow down for cars because it's not monitoring the lane. You might see the lane on your screen, but it won't ASSUME anything at least not in its current state.
If you have lanekeeping on, it tends to look "around the bend" better.
But in this case, yes, you probably wouldn't get warnings for this. Not to say that maybe lane assistance stuff should've kicked in too, but unknown what that was set at.