Quoting Cal's Opening Post: Against it: Xcano, Aiden, LAS, Blue, Assaltwaffle, and Imaginym (I think)
Since I'm mentioned, presumably because I posted in the calc's blog page, I suppose I should try to make my stance here clear, for all that that matters. Hopefully I'm not too late.
The calc's basis is that of an animation involving stormcloud creation. I don't see much wrong with using animations. Especially given this recent thread:
https://vsbattles.com/vsbattles/786524
My concern with this is why we'd only apply it to the Tier 7 Pokemon & above. I understand that's where the results of the calc place it at a minimum but trained Pokemon aside....
Well, barring special cases like Groudon who has it via other means (& a higher tier anyway, but not the point of Groudon as an example here.) only a trained Pokemon would know this if it didn't learn it via level up.
Trained Pokemon are already known to be stronger than wild Pokemon.
It just seems odd to exclude some of the Pokemon who learn this naturally, in the wild/via level up from the upgrade.
The Pokemon that learn it via level-up.
Here's a blog Cal made about Pokemon scaling for reference.
The Pokemon that aren't currently Tier 7 that learn it via level-up:
Pikachu (Games). Aside from the minor oddity of using a game animation calc to upgrade Ash's Pikachu in the anime, I see little issue with this.
There are instances of cloud creation for Thunder's use in the anime anyway. Even not for Pikachu, sometimes.
Jolteon, Electabuzz. Fully evolved Electric-types (At least, Electabuzz for 3 generations.) who according to Cal's Blogs are MCBL+, so I suppose, ineligible, despite being very close to being Tier 7 otherwise.
Flaaffy is also MCBL+ but Not Fully Evolved & Electabuzz scales to Electivire & Elekid.
Mareep, Electrike: First stage Pokemon with little to scale to nor feats, & thus, Pokemon whom I doubt there's issues with not giving Thunder scaling to.
Elekid: Probably shouldn't scale to Thunder use. Baby Pokemon aside, it scales to Togedemaru, which [Togedemaru] along with other "Pikaclones" (Similar design themes, romanized Japanese name in English, Electric rodents, but otherwise different species.), is given Pikachu's tier for being a Pikaclone, despite all Pikaclones except Pikachu being Pokemon that don't evolve to or from anything.
Heliolisk: MCBL+ by the scaling in Cal's blog but not much else
& Wall Level to Building Level by calcs for its feats, lol. It & by extension,
Helioptile couldn't get the scaling from this either.
Plusle, Minun, Dedenne: The so-called Pikaclones that learn this move, unlike Pachirisu & Emolga. Although, unlike Pikachu, they're also Pokemon that don't evolve & thus don't have any pre-evolutions they're stronger than, nor evolutions they're weaker than. With that in mind, I find it a little questionable that even wild instances of this Pokemon can learn & wonder if they should be able to get the upgrade.
Also, IMHO, applying it to Pokemon shown using it seems fine, but (for the most part) not those who aren't show using it & only learn it via means other than level-up, just to make my opinion clear.
Also, one Pokemon I'd like to make mention of is Clair's Dragonair. This Gym Leader-trained Pokemon actually created thunderclouds at the least, & may have used Thunder also.
I haven't checked the episode yet, but:
Trying a different approach, Clair orders Dragonair to summon thunder clouds while Charizard keeps Dragonite busy.
It was a Very Well Trained Dragonair, I'll admit, but it's also worth mentioning that, besides Dragonair learning the move by TM (& sadly, only TM.) it has numerous Pokedex entries mentioning it being able to control weather, &
even a wild one stopped a storm that produced at least one lightning bolt if my memory stopped.
I'd question if this wouldn't also be applicable to Dragonair, & by extension, Dragonite.