In addition to my questions from a couple of posts before, here are a few more I’d like to ask:
1. Could you please confirm about the authorship of Sarvastivadin abhidhamma books? I mean, perhaps we are comparing apples and oranges here because Theravadin abhidhamma books are ascribed to the Buddha, while Sarvastivadin apparently are not – this comes from a post by Bhante Dhammanando on DSG (#81054):
the authorship of each of the seven books in the Sarvastivadin
Abhidharma Pitaka is attributed not to the Buddha but to one or another of the
early patriarchs of the Sarvastivada school. I don't think they ever claimed
that their Abhidharma was buddhavacana, and indeed their third Basket is most
often called the "Shastra Pitaka", strongly suggesting an origin in the form of
Moreover, for the Sarvastivadins (and Sanskrit-based Buddhist schools in
general) 'abhidharma' didn't mean what 'abhidhamma' means for the Theravada.
'Abhidharma' for the sanskritic schools meant any further discussion of dhammic
topics by bhikkhus after the Buddha's parinibbana. If you look, for example, at
Vasubandhu's Abhidharmakosha, you'll see that virtually anything can be an
'abhidharmic' topic for the sanskritic schools. Although aggregates, elements
and sense-bases are a major theme in this work, there are also discussions of
Vinaya minutiae, history, aesthetic theory, and many other themes that a
Theravadin wouldn't see as specifically abhidhammic.
2. On a related matter, I’m a bit confused about the timeline you suggest and the conclusion that all the early schools had only Sariputta abhidharma sastra in common as a sort of a proto-abhidhamma work, and then each school developed additional books on its own as they spread through India in Asoka’s time:
The Sariputra Abhidharma Sastra structurally is very, very close to the Theravada Vibhanga (and a bit of the Dhammasangani) and also the Sarvastivada Dharmaskandhapada Sastra.
One very good argument to explain all this is: Between the first schism (second council) and the time of Asoka (third council), there was a large group of Sthaviras around the area from Mathura - Avanti, east of the old heart of the dispensation, and slightly south too. While they were here, they developed possibly a couple of forms of "abhidharma", which are "about the dharma", and basically forms that were very similar to the Vedallas, and Vibhanga suttas, and also the newer Upadesas. These actual suttas were taught by people like Sariputra, Mahakatyayana, Ananda, etc.
Now, during Asoka's time, when the various groups spread out across India, these Sthavira groups took the proto-type Sariputra Abhidharma with them. Because the Theravada ended up so far away, and likewise the Sarvastivada in Kasmir, they developed rather independently, and bear less similarity over time. In central India, the groups like the Vatsiputriyas and Dharmaguptas maintained more commonality, hence their Sariputra Abhidharma Sastra was used by a couple of schools.
This doesn’t make sense, because, afaik, 7 Theravadin abhidhamma books were already closed at the Third council, so before, or at the time when different schools (notably Sarvastivada) went their separate ways (geographically and philosophically speaking).
Further, the fact that Taisho Tripitaka contains only Abhidharma sastra of Sariputta that's ascribed to Vibhajjavadins (as per Chinese canon page on buddhanet) doesn’t have to mean that this was the only body of abhidhamma works that Vibhajjavadins developed while Sarvastivadins still had geographical contact with them. I mean, an equally valid theory could be that Sarvastivadins took only Dhammasangani and Vibhanga (as embodied in Abhidharma sastra of Sariputta), and eventually discarded (or simply forgot) the rest as their later abhidhamma works developed.
For example, the majority of books I come across on abhidhamma in English likewise deal only with the material from Dhammasangani and Vibhanga, and occasionally a bit from Patthana. The other 4 books from Abhidhamma pitaka are rarely mentioned or just declared too complicated. So, perhaps the situation was exactly the same back then – people took with them only what was simple enough and discarded the rest...
Anyway, please point out if I’m wrong somewhere. Thanks.