Forgive me, PT6A, your friend might well be right but their explanation is very long winded and not that clear to me.
I am always confused when pilots go selected speed to kill G/S mini to “stop the A/THR reducing thrust” because I find that G/S mini works well in gusty conditions. This is my understanding of it:
Consider a hypothetical day. A Boeing and an Airbus FBW which are both fully configured at 6 miles, are making simultaneous parallel approaches to parallel runways. Vapp for both is 140kts and the wind is calm, so both have a ground speed of 140kts.
A 20kt headwind gust appears:
The Boeing reduces thrust to keep the IAS at 140kts; its ground speed is now 120kts.
The Airbus increases thrust and airspeed to 160kts; its ground speed is thus kept at 140kts.
The headwind disappears back to calm:
The Boeing now has an IAS of 120kts and its engines are at idle. Its ground speed is 120kts.
The Airbus has an IAS of 140kts and its engines are spooled up. Its ground speed is still 140kts.
A 20kt tailwind gust appears:
The Boeing increases thrust to keep an IAS of 140kts. Ground speed is now 160kts.
The Airbus reduces thrust but it does not allow its IAS to reduce below 140kts. Ground speed is 160kts.
The tailwind gust disappears back to calm.
The Boeing now has an IAS of 160kts, a ground speed of 160kts and its engines are spooled up.
The Airbus has an IAS of 140kts and its engines are at idle but its ground speed is still 140kts.
So, when the gusts disappear; the conventional aircraft is at either - 20kts with engines at idle or + 20kts with its engines spooled up. The G/S mini aircraft is at either - 0kts with engines spooled up or + 0kts with engines at idle, so it does not deviate as much for the same changing conditions.
I think some “conventional pilots” get confused and nervous about IAS and the speed target changing so much with changeable winds, but G/S mini gives a safer energy state.