110 psi is considered good compression on a UCE which is ridiculously low by any other standard.
Seems, then, it's more like a compression reducer - there will always be some compression built up with each revolution, because the piston is still traveling upwards after the decomp closes...
Nice Desi! Cool that someone finally tore it all the way apart and figured it out. Nice work.
It's primary function is to keep the piston from kicking back and reversing the crankshaft rotation during engine shutdown.