"Symptoms" are self-reported. Symptomatic seroprevalence is objective.
What this should tell you is that "symptoms" are a bad endpoint for a randomized-controlled trial, not that if the good endpoint doesn't show you what you want, you should rely on the bad one.
It said that it can’t support an impact of cloth masks usage on infection rates, but associates them with reduced severity/symptoms.
That’s a notably distinct proposition from “no effect.”