Perhaps you could expand on “It makes sense that the Sarvastivadins would remove it…”
Sylvester’s argument was as follows:
http://www.dhammawheel.com/viewtopic.php?f=25&t=26456#p380455
… the loss of the "The All exists"and “The All does not exist” passages proved particularly acute for the Northern Buddhists, as their sutra became dislocated from the pre-Buddhist context. It does not help that SN 12.47 and SN 12.48 do not seem to have survived in the Agamas either. Even if echoes of the Upanisadic “sarvaṃ asti” survived in the memory of the Northern schools, it did not help that the Sarvastivadins adopted a similar-sounding but unrelated motif, which gave rise to so much spilled ink over the issue of svabhāva that detains Ven Nanananda today.
Let it be said - the Buddha was not in the least bit interested in the question of own-being or essence of dhammas.
If we accept the reordering of SN 12.15 above, then the Pali version would read:
… But for one who sees the origin of the world as it really is with correct wisdom, there is no notion of nonexistence in regard to the world. And for one who sees the cessation of the world as it really is with correct wisdom, there is no notion of existence in regard to the world.
‘All exists’: Kaccana, this is one extreme. ‘All does not exist’: this is the second extreme.
Without veering towards either of these extremes, the Tathagata teaches the Dhamma by the middle: ‘With ignorance as condition, volitional formations come to be; …
The Northern versions omit the bolded part. Admittedly, this is not a huge change but if it is omitted then the extremes are the notions of existence or non-existence, rather than “All exists/All does not exist”.
I agree it may be too obscure a point, and perhaps Sylvester could clarify.