The expectation is that FV consumption decreases all cause mortality.

This agrees with the observation that low-pesticide residue FV intake was inversely related to all-cause mortality.

If High-pesticide-residue FV intake was unrelated to all cause mortality it could mean that there is a detrimental effect in High-pesticide-residue FV that offsets the expected benefit of FV.

Inversely related to mortality. I.e low pesticide intake reduced morality.

I'm still confused. Morality or mortality?

If you eat low-pesticide fruits and vegetables, you're less likely to die. If you eat high-pesticide fruits and vegetables, your chances of dying are unaffected, which is surprising because you would expect that increased fruit and vegetable consumption would decrease your chances of dying. So, it seems that the potential health benefits of eating fruits and vegetables is negated if they contain high levels of pesticide.