Hans have studied this line because Magnus played it before. Was the line exactly the same: no, he explained that he spent several minutes to evaluate if the transposition was possible. I'd rather believe Hans than the far fetched cheating theory. Magnus just was on full paranoia mode. Everybody agrees that both of them played poorly and that Hans even gave situations where Magnus could have won.
He is not in charge of maintaining a chess database. Did Magnus played this before: yes. Can Hans have know about this: yes. Can he have studied this line because Magnus played it before: yes. Was the line exactly the same: no, he explained that he spent several minutes to evaluate if the transposition was possible. Very credible (contrary to Magnus insinuations)
It was a line that Magnus has already played once or twice in tournament. Hans wondered how Magnus could surprise him. So Hans studied various lines rarely played by Magnus including this one. This was very clear in Hans interview.
Copycats ! I've released a small library to display cross-platform dialogs (because I couldn't find what I needed) and 2 weeks later a copy cat released a similar Library/API but based on a different approach. In the next years, at least 2 other competing projects joined the party. Mine is tiny file dialogs.