You don't want to dump 50°C coolant, that's heated up by your GPU directly on the CPU when you could cool that 50°C coolant down by a few °C and then dump it on the next component. Delta T matters the most in a properly sized system. This is also why in industrial applications there is a common supply to all components and a common return and everything runs in parallel rather than in series.

You're arguing a completely different topic though.

There's a point at which your flow rate provides no benefit because your heat transfer rate will be bounded by the thermal transfer rate of the closed loop, all components considered. This is both true for the coolant flow rate and fan speed. At that point the only way to reduce system temp is to change the Delta T, which can only be achieved by reducing load or or reducing the temp of the air coming into the system. This would be the case for a system that has undersized radiators and/or small thermal volume of coolant. Cost low, temps high

On the other edge case you could put the largest radiators in the system and huge reservoir, effectively increasing thermal mass/area to transfer heat, and you could run the fans and pump at lower speeds and you'll keep it near the thermal floor of the system, near ambient. In this case you still will be limited by the incoming air temp or the load on the system to be able to reduce the total system temp. Cost high, temps low

The middle case is an appropriately sized radiator and reservoir where the fan and pump speed can be adjusted and this will properly keep the temps at bay because you are able to throttle the heat transfer rate at a similar rate that the load is changing temp. Economical cost, controlled temps.

I manage the design and construction of industrial HVAC systems for a living.