Bottom line = keep the oil clean with consistent oil and filter changes.
The way he talks, either he will have a plugged oil filter with little or
no oil flow, or contaminated oil making it's way thru the whole engine.
Leave the bypass valve in and change oil more often, and if you suspect
a faulty bypass valve, replace that sucker! Also maybe if you're that
concerned with the level of contamination in your oil, send a sample out
for analysis! Just my 2 cents ....................
Andy