Hey Jasom, welcome, and I appreciate that you seem like an intelligent and reflective fellow. But I don’t know how many times I need to say this: Waharaka views are nonsense. They are the flat earth of Buddhism.
Imagine that you were sitting in your kitchen with a friend. And a cat came in. So you said, “Nice pussy cat!” Your friend says, “Aww, she’s so pretty. Except, you know, it’s not really a cat. It’s a rat.” “I’m sorry, what?” “Yes, yes, the word that you think means cat is actually a rat.” “But … I don’t know what you mean.” “You see, the dictionaries have it all wrong. I have a special language beam in my brain that tells me what words really mean. So that’s how I know. A cat is a small rodent, and a rat is a small feline.” “But no, that’s not how language works. You can’t truly believe that everyone who speaks English, who ever has spoken English, simply gets the meanings of basic everyday words wrong.” “Yes, that’s right. For so many years, everyone who owns a rat has been calling it a cat! Funny, right?” “Not particularly. It’s crazy! That’s not how language works, like, at all. Language is about shared meaning for communication in a group. It’s not beamed into your brain. My friend, that’s not mentally healthy.” “Ahh, well, I see the problem. You’ve been trapped by the system. You just believe everything you’ve been told. Have you ever considered that maybe you might be wrong? That the experts don’t know everything?” 
To be clear, this seems like an exaggeration, but it really isn’t. It’s literally what the Waharaka folks do. No-one with any understanding of language will ever see it as more than a bizarre upside-down world. Forget about them.
Yes. I have made this a cornerstone of my meditation teachings for the past several years. The “objectification” of meditation is, in my view, the single biggest hindrance in progress.
Not at all, we’re here to have a conversation!
That’s true to some extent, although in the case of the Mahasanghika BHS, the language itself is later than Pali. But in the Mahavastu, in particular, we see a conglomeration of texts from many sources, with little attempt to reconcile them, so it seems likely that we have old texts there. There is, for example, an extra verse in the Ratana Sutta which appears authentic.
translation:
text:
http://gretil.sub.uni-goettingen.de/gretil/2_pali/3_chron/dipavmsu.htm
(search mahasangitika)
In the Dipavamsa, the Mahasanghikas are called Mahasangitika. That they are in fact Mahasanghika is proven by the fact that they are said to split into Gokulikā and Ekabyohāri, known subschools of Mahasanghika.
Indeed, in fact my argument was really about the Pali Abhidhamma. The northern Abhidharmas are quite different, and often much more useful. For definitions of technical terms, my go-to is Asanga’s Abhidharmasamuccaya.
We do, although AFAIK these were much later; the Abhidhammatthasaṅgaha being the most important. I wonder if they were inspired by the Sanskrit texts?
Obviously a broad and long thing like the Abhidhamma has many dimensions and can’t be trivially reduced. The real point of my argument was to counter the reductive notion that Abhidhamma is an unimpeachable source of absolute truth, and to show that it serves many roles in a community that are far from rational.
Thank you for saying this. I’m sure there are many people reading this who are like, what, why is everyone so uptight about these silly ideas? But this is a pattern that’s been repeated everywhere: in Perth, in Sydney, on it goes. It’s exactly like the various kinds of conspiracy spreading in the rest of the world, just with a Buddhist flavor. It’s silly and toxic. There are real problems in the world, and Buddhists are wasting their time on this nonsense.
You noticed that too?