Sorry, but you've given bad advice about this without a full understanding of how it works. My intent here is not to slam you, but to hopefully explain a more complete picture of what's going on and why gas flow restriction does work.
Pressure at the gas port is NOT the problem, or at least not the deciding factor as you seem to think. Pressure in the bolt carrier, and timing to reach that pressure, is what's important; the BCG requires a certain amount of gas pressure to overcome the force needed to unlock* and metering gas flow causes that pressure to build slower. A restriction of any kind (gas port size, AGB, etc) affects the rate that gas feeds back to the BCG, and therefore the timing before it unlocks.
This is not a static system, far from it; in a dynamic system like this the supply pressure (at the port) is only one factor in determining pressure in the final stage (the BCG). In a dynamic system, gas flow and pressure are directly related; restricting flow from a high pressure chamber to a low pressure chamber delays pressure buildup in the secondary chamber and can restrict the total pressure buildup if the system does not reach a static state.
*The force needed for unlocking is also dynamic and not a static number; as pressure drops in the chamber the necessary force also drops. Obviously the goal is to delay unlocking until that force is at it's lowest possible point while maintaining reliability.
All that to say, yeah he can fix the issue with gas adjustment. It doesn't do exactly the same thing as a longer gas system, because the pressure supply still begins earlier, but the gas flow can still be metered at a lower rate, limiting gas volume and pressure (which are directly related) at the BCG, and therefore unlock timing.
