Magnus didn't play particularly well and Hans played ok. This was not an example of a superhuman intelligence passing hints to overcome Magnus at his best.
I don’t totally buy Hans didn’t prepare the weird line, but it’s worth calling out; it’s at least marginally possible that Magnus out himself in an unwinnable position on purpose, but couldn’t convert it.
Everyone says this, but do you really know? Those statements are after-the-fact observations of engine evaluations. They don't speak to the amount of mental work that Hans would have had to put in to play optimally (or 'ok' as you say) in those positions.
You might find yourself making the same remarks when looking at the post-game analysis of any top player against an engine. Everyone crumples eventually against perfect play.
Yes, they do. When Magnus makes poor choice - not giving himself an advantage or playing moves giving black an advantage - it makes it easier for black. That’s the whole point.
Putting your opponent in positions that are better according to the engine but only with engine-like perfect play is a strategy at the highest levels of chess. Because the move is objectively worse, it won't be played, because it's not played, your opponent won't know it, because they don't know it, you'll play it better, then you win.