Of course there are other factors, it could be the way the alternator was wound at the factory, a different voltage regulator, or one of a dozen other things, maybe it was built on a Wednesday. Like you said,
you don't know. Yes they are all the same truck with small differences. I discovered my MPX (interior fuse block) is different than that of older and newer model Trail editions. Go figure.
I was one of the few that suggested a secondary boost (turns out I didn't need it just the better diode). Maybe it has to do with the fact I a have a trail w/ 130a alternator vs. the stock 100a. Not sure, all I know is, I hover around 13.5 - 13.7 @ the terminals w/ variable RPMs using a single diode (GM or HKB). Which is what they suggest for a trickle charge on an Odyessy AGM. Charge is 14.3 to 14.7 (at a suggested 40 amps). With the arclight2.0 in
Boost (not over boost) I get 14.48 @ the terminals, highest and average 14.2. Concurrently, Techstream reports 13.80 highest and averages 13.20
I have yet to plug in my trickle charger since. YMMV
You called it out twice on cost, it is a waste of money you said. I called you on it, that's all, not trying to be a dick, that is just how it read. The Wally World was a jab at supporting one man local business Vs. feeding an ever hungry giant. Apologies for not being more clear.
I am a big fan of keep it simple (I had a base model '89 hilux for 25 years, no power anything, no a/c, fuel injected 22-re 4x4 manual, doesn't get much more simple apart from natural aspiration, loved it

). It seems simpler to use this and a readily available 7.5 amp fuses. Custom diodes are all fine and dandy, particularly when you sell/trade the truck and the next guy has no clue what's up. I am pretty sure, if that time comes, I will remember to pull this out and replace it with a stock fuse.
You do what works for you, doesn't mean you have to say its a waste of money, or unnecessary or, a POS (I know you didn't say that), or whatever. Right?