One of the things that puzzles me about these statements, in terms of getting reasonable items, is that older adventurers are packed full with magic items. Often, especially with rings, those items are certainly not level appropriate. It almost seems like some are saying that if the player wants that sword X they that is already part of the packaging, they'll go out of their way to switch it to something not desired by the player. "oh, he wants a +2 two handed sword does he? Even though this prewritten adventure has one here I'm changing that to a +1 great trident. Screw him! He wants that sword he'll hunt it down to Odin's halls!"
Since you quoted me, I have to ask: Huh? How do you get that from what I wrote?
If I'm using a module (which is fairly rare; I mostly write my oqn adventures) I'll likely let the items in it stand, unless I feel them to be really ridiculous. I would no more change an item to screw a player than I would change it just to benefit a player. Also, since I play an older edition of the game, I don't really have any hard and fast rules about what items are "level appropriate". I merely consider how items will affect the campaign.
OTOH, in the case of a +5 sword or a staff of the magi, it seems logical that if such an item was lost, was known to be lost,
and is still lost (i.e. not in the hands of some high level NPC) that its likely in the possession of something pretty nasty, or deep in a dungeon or other very dangerous area. If low level PCs want to go after that item regardless of what they learn from research or sages, fine - let the dice fall where they may. Maybe they'll luck out. But lesser-powered items (a +2 sword or a staff of striking ) are more likely to be in less dangerous locales.
In terms of the game as written, how far is it stretching it, in any edition, to make these item swaps? What if the power level of the item players find in the random loot is higher. Has the GM shown that random loot is superior or does lack of even acknoledging the wish list existance prevent them from even knowing it?
The wish list sever several types of wish fufillment ranging from mechanical bonuses to themes in my opinion.
Its the principal of the thing. I'm the referee; I don't favor the players, nor do I seek to "defeat" them. Of course, I actually want to see them triumph, but I don't change things to allow them to win; they stand or fall on their own merits - and on luck. Likewise, if they find the item that they want in some monster's hoarde (or pry it from some villain's cold, dead fingers) good for them! But if they want a specific item they need to control their own destiny and quest for it.
Also, the wish list thing seems to me to ruin verisimilitude.