I offered no opinion about whether it was difficult or not. I responded to your claim that there was no physical meaning to the scaled reading of the average rectified value, and your claim that nobody would design an instrument to output this value.
Coppice's point is that the only reason it's designed that way is because True RMS is difficult. No-one would willingly design a scaled averaging meter unless budgetary or design constraints force them to, which makes it a strange thing to actually want/go out of your way to get.
If that was his point, he wasn't very clear about it.
It looks to me like his point is "Nobody would sit down and try to develop an instrument specifically to output this value." BECAUSE "...scaling the rectified average to be like the RMS would be for a pure sine wave is simply a botch without any physical meaning."
Furthermore, TRMS is not difficult; you just have to use the right meter movement. Moving iron, thermocouple and electrodynamometer movements inherently respond to TRMS AC+DC.
VOMs used a D'Arsonval movement because they wanted greater sensitivity to DC voltage and current, and ohms measurement. Having made that choice of movement, it was necessary to use a rectifier type AC measurement. Back then the waveforms they were measuring were usually sine waves since there were no highly distorted waveforms such as you get from a triac light dimmer, for example, so the rectifier type AC meter did the job.
The usual measurements of grid related voltages don't need a meter with a high input impedance, so there is no need to use a high sensitivity D'Arsonval movement. Any movement is suitable for measurements of grid powered loads. Notice that even the VOMs with D'Arsonval movements have fairly low input resistance for AC voltage measurement. For example, the input resistance for AC measurements on the Simpson 260 was 1000 ohms/volt, versus 20,000 ohms/volt for DC voltage measurements. This is not a problem when measuring grid related voltages where there is plenty of power to operate the meter.
The reason VOM's AC measurements were made with a rectifier type method is not because TRMS measurements were difficult.
When a meter was needed that was not a combination meter like a VOM, but was only a voltmeter, it was easier and cheaper to use a TRMS responding movement such as this, rather than the more complicated rectifier type:
Here's an example of a multipurpose analog meter that measures volts and amps, TRMS, with .5% accuracy: