Blackbird is exactly right. I just tested my Insight. A loosened oil cap did not “blow off” the filler hole (it just sits there vibrating), but when the cap is totally removed, the “windage” feels like a breeze coming out. You feel the pulses coming out, but not the pulses going in.
Edit: Begs the question: why would an inline 4 pulse so much (2 pistons going down while 2 pistons going up)?
You will get a breeze. Crankcases do develop pressure by virtue of the blowby. But my impression of the OP’s description is that he was describing more pressure than that. A compression test would put the question to rest. If there’s no issue, no harm will have been done. If there is more pressure than there should be, it’ll show up on the compression test.
Nobody is suggesting tearing into the engine, just performing a compression test. I believe Honda overreacted.