With today's variable output oil pumps, flow volume is a matter of software and very likely, a pressure sensor, although even that's not "for sure". When the farthest cam bearing in an OHC/DOHC engine is starved for oil, it is likely due to no-flow conditions at that bearing cap. Despite normal flow rates through the pump.
Ultra low viscosity oils can, in some situations, be responsible for shorter engine life. I'm simply bringing up one way this can happen. Things are fine, right up until they are not.
I've mentioned oil lubricated chains many times. Manufacturers now use coated pins and parts to extend chain life with ultra low viscosity oils. As we might expect, this improves chain life markedly. Unfortunately, the coating has a lifespan too and once used up, chain "stretch" is rapid.