Maybe he was sick, but this is not the lowest percentage he has shot in a game this season. He had 2 separate regular season games with a worse shooting percentage and one of those he took 14 shots making just 2 (so it wasn't a small sample size). He had 5 separate regular season games this year where he was 30% or worse from the field and in 2 of those games he had 21 shots (making 6) and 17 shots (making 5).
This also isn't the first time he has been terrible in the playoffs. His last year in Cleveland he was 4 of 17, 6 of 19, and 7 of 21. Even one of the finals games he was just 8 of 23. The year before that when Cleveland won the title he had a lovely 3 of 19 game against the Raptors in the ECF. He also had 3 separate finals games against the Warriors where he was 7 of 22, 5 of 14, and 7 of 18. Even that first season where he ended up missing a lot of games, he was pretty bad in 3 games going 2 of 10, 3 of 13, and 3 of 11. In other words, Kyrie has pretty consistently throughout his playoff runs put up some pretty awful shooting performances.
So yeah there is amazing playoff Kyrie, which we see at times (like game 1), but there is also the playoff Kyrie that is downright terrible (like game 2). And again maybe he really was sick, or maybe it was just Kyrie being Kyrie and the writers are trying to make excuses for his otherwise poor play.