Imbue Item ignoring prereqs y/n

[Gruftzwerg]

Somehow i think you're just ignoring certain points by now. Not everything to do with spells is an "altered cast". The "casting a spell" rules are not a base template that is then tweaked a little bit, as you are suggesting There is literally no proof for it. The "primary source rule" shtick you keep trying does not work because it does not apply here. There are no rules contradictions, and also yes, the book LITERALLY says that you are doing something that is not casting. You seem to be confused, thinking that the book has to say the words "you are not casting this spell" in order for you not to be casting when it literally says in several places that the thing you are doing is not casting. The book doesn't say you are casting it, but in a different way, and it has to say that in order for you to be right. The rules have to tell you what you are doing, they don't expect you to do the mental gymnastics you are doing just to be right.

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You are still ignoring the territories the Primary Source Rule sets:

... The Player's Handbook, for example, gives all the rules for playing the game, for playing PC races, and for using base class descriptions. If you find something on one of those topics from the Dungeon Master's Guide or the Monster Manual that disagrees with the Player's Handbook, you should assume the Player's Handbook is the primary source. The Dungeon Master's Guide is the primary source for topics such as magic item descriptions, special material construction rules, and so on. ...

"Casting a Spell" sets a general rule when you want to use spells. And there are only 2 options that can alter this:
a) mentioning an explicit rule change/update that is like Rules Compendium, Draconomicon or Errata as examples.
b) make explicit call outs for specific rules that only apply in a niche
If you want to use Spells in any way, the "Casting a Spell" rule is the gatekeeper. SLAs alter the component (V,S,M,F,XP) rules. Spell trigger items do the same. And crafting is in no way special worded that it denies the status that a spell cast is triggered here. It doesn't need to mention that it is still a spell cast. PSR demands that it needs to deny it clearly to make your interpretation plausible.

I'll try to give a real life "light switch" example here for "trigger":
Imagine a light switch (cast) for a light bulb (spell) that you can use actively as "normal" (general) and that can also be "triggered" passively (specific) via the daylight (when it becomes dark).
Unless the "trigger" has some special functions (explicit specific exceptions), you expect the switch to work as intended.
It is still "triggering" the light switch (cast) that activates the light bulb (spell).

As said, a trigger only does what you would normally expect as outcome, unless specific exceptions are called out (and build in^^). And so far the crafting rules only show how parts of "casting a spell" gets altered, but it never denies its status as spell cast. And it doesn't define a new status either. There is no explicit mentioning of that (or did I miss any crafting specific definition paragraph about "trigger" anywhere? kindly asking here).