Just because someone is famous, respected, etc doesn't make them infallible or immune to perception bias.
It might actually be even worse for well-respected experts in some contexts. If you're good at something, it make sense that you're probably right about a lot more things than you're wrong about....and that feeling will stay even if the things you're right/wrong about don't matter to how good you are. IDK....it's hard to explain.
OOPS: We're talking reverb & delay here, not two delays, so I'm giving a wrong example?
Delay is perhaps easier to understand, but it actually can be a little different depending on the order if the delays aren't the same.
First, let's look at the delay times. If you just click the strings by hitting them while you're palm or left-hand muting instead of sustained notes and you have a 100ms delay followed by a 150ms delay, each set to give 3 repeats.
With only the 100ms delay, you hear clicks at: 0, 100, 200, 300, and then it stops.
With only the 150ms delay, you hear clicks at: 0, 150, 300, 450, and then it stops.
With 100ms > 150ms delays, you hear clicks at:
Original sound: 0
Shorter first delay, from the original sound: 100, 200, 300
Longer second delay, from the original sound: 150, 300, 450
Second delay, from the first delay's first repeat: 250, 400, 550
Second delay, from the first delay's second repeat: 350, 500, 650
Second delay, from the first delay's third repeat: 450, 600, 750
So, the full set of what you hear is at: 0, 100, 150, 200, 250, 300(x2), 350, 400, 450(x2), 500, 550, 600, 650, 750
If you reverse the orders of the delays, you hear:
Original sound: 0
Longer first delay, from the original sound: 150, 300, 450
Shorter second delay, from the original sound: 100, 200, 300
Second delay, from the first delay's first repeat: 250, 350, 450
Second delay, from the first delay's second repeat: 400, 500, 600
Second delay, from the first delay's third repeat: 550, 650, 750
So, the full set of what you hear isat : 0, 100, 150, 200, 250, 300(x2), 350, 400, 450(x2), 500, 550, 600, 650, 750
At least as far as the delay times go, they're the same.
The first few repeats will sound different if, for example, the delays themselves sound substantially different. If one of them is significantly darker than the other, for example, then which exact repeat times are bright vs dark will change. In the way I listed the times above, the last 3 lines of each ("Second delay, from the first delay's....") will have the effect of both delay sounds (e.g., not filtered, then dark, sounds dark...or dark, then not filtered, sounds dark). But, the times listed in lines 2 and 3 (each delay from the original sound), will swap which ones are not-filtered vs dark, depending on which one is dark vs not-filtered.
If your 100ms delay is the dark one, then the sounds at 100, and 200 will be dark.
If your 150ms delay is the dark one, then the sounds at 150 and 450 will be dark.
Because 300ms comes from both of them (in this example), it'll be in-between because it's pretty literally half-filtered. It'll also be louder than the other repeats.
All of this assumes perfect clocks.
Swapping one of the delays for a reverb makes the times a lot more complex to actually list...but the same thing basically happens.
The "tone" things (which I exemplified by saying dark), are probably easier to understand with a Delay and a Reverb if you really try to imagine/visualize it. But, because each of the reverb and the delay have their own tones and they "combine" more simply, you don't get that weird thing with the first few repeats changing tonality.
You'll get similar changes in sound from changing the order if one of the delays is modulated or has a broken/flawed clock, but that seems like it makes it not time-invariant (another necessary condition for the order not mattering). Which means that it also wouldn't be the same for a modulated reverb or something like Shimmer reverb. Again, those are not time-invariant effects.
Hopefully, that all made sense.