I dont mean to imply he is worried for nothing, but it was just went from fighting to MC's first thought immediately after was about procreating. Was a tad jarring. The fact the fight went kinda went from "Oh this fight wont just be a easy one, this might get serious" to just "Hope u can swim in lava lol" probably didnt help make it less jarring.
Now that I think about it, yeah it was more so I expected a real serious fight for it to kinda just be breezed over and MC just say the only people stronger than him are god like creatures that never show themselves so he realistically has no worry unless he angers them that was more jarring.