My thought on the most likely confounding factors is both requirement and proclivity to get tested. Vaccinated/boosted folk are more likely to be in situations requiring testing, thus finding more mild or asymptomatic cases. I'm not sure on who is more likely to get tested of their own volition for mild symptoms and could see arguments both ways, but could see it being a factor.

Agreed, the deaths by vaccination status shows a stronger benefit, particularly with age.