That still doesn't mean it lacks concrete objectively measurable symptoms.

"...In this cohort study including 100 patients recently recovered from COVID-19 identified from a COVID-19 test center, cardiac magnetic resonance imaging revealed cardiac involvement in 78 patients (78%) and ongoing myocardial inflammation in 60 patients (60%), which was independent of preexisting conditions, severity and overall course of the acute illness, and the time from the original diagnosis....."

https://jamanetwork.com/journals/jamacardiology/fullarticle/...