I can't honestly say I'd ever considered the argument that a bunker that's too deep actually lessens the temptation/decision-making involved. But that said, I think I can see how that argument ends -- or, at least, how that argument did end at dozens of courses I've played over the years:
"Let's make this fairway bunker deep, quite deep, but not so deep that the golfer immediately knows he can't get a long iron out and to the green, and so automatically lays up or pitches out sideways instead".
-- "Great point there, GB! We always want to give golfers options and choices! Okay, deep but not too deep. I'll get right on it".
"Wait!".
-- "Yes, GB?"
"On the other hand: if the bunker is a deep one, and even if it's not too deep, the good player might be tempted to hit a mid or long iron out of there, but the mid-to-high handicapper will just have to pitch out sideways all the time anyway".
-- "I think I see where you're going with this".
"Do you see what I mean?"
[Pause]
-- "Actually, ah, no, I don't."
"Look: it will be just another example of the already better golfer having even more of an advantage over the weaker golfer."
-- "Oh, I think I get it, yes".
"It'll be the same as holes that are too long, or greens that are too small. A deep but not too deep bunker can be handled by the low handicapper but not by the higher handicapper. For him there'll be no choice or option at all".
-- "You're right, GB! Why didn't I see that myself?! What happens then is that the 'course isn't playable by all'".
"That's right".
-- "Oh, that would be terrible, just terrible! Didn't the great Dr Mackenzie himself say that a good golf course has to be playable by all?"
[Pause]
"So. What to do? What to do?"
[Pause]
-- "GB, I may have an idea. If you don't mind, I mean, I'll just toss it out there for whatever it's worth".
"Go ahead".
-- "Well: how about a bunker that is 'deep', but not only is it not too deep, it's also 'not actually deep at all'?"
[Pause]
"You mean: a 'shallow' fairway bunker?"
-- "Ah, not quite: I didn't explain myself very well. I don't necessarily mean a 'shallow' bunker, necessarily. I mean a deep bunker that is not, actually, in reality, very much or so much deep at all, or even 'deep' -- as the concept is normally understood".
"Hmm. You mean: a 'not deep at all' deep bunker"?
-- "Yes, exactly! You said it perfectly! A deep bunker that is not in any way at all, nor could ever be defined as being, 'deep' -- in the conventional way the word is usually used, by non golf architects and their ilk."
[Pause]
"Okay. Okay, I can see that. Let's try that. Let's give it a shot. We'll see how it works".
-- "I'm right on it, GB! This is going to be great, I know it!"