This is not a roof I inspected. It happens to be one my neighbors’ roof! He “knows everything” and had an already underventilated cathedral roof whose shingles only were replaced 3 yrs. ago when he moved in. The plywood was deteriorating (black etc.) and the soffits were mostly blocked!
So he gets ice dams, water infiltration etc. and decided to “caulk the shingles…”
Dumb and dumber…