its not bullets expended its bullets connected - e.g. 4% of his shots that connected were headshots
even if he spammed smokes and didn't connect it doesnt count towards hs percentage i p sure
i mean, he was playing raze, and everytime he hits something with the painshells, the game counts it as a bodyshot, along with the rest of her utility, so I wouldn't pay much attention to that stat
his ult as well, he got that boombot kill and an ult kill as well as any nade kills he may have gotten. that on top of a bad game will give you a bad HS percentage