Lindil
For better clarity maybe, I'm talking about characterizing (for example) Qenta Noldorinwa as an internal variant to later versions of the same text; that is, external and superseded drafts being recharacterized by readers as collectively internal, and the Subcreated World is thus made inconsistent where Tolkien himself imagined no such inconsistency.
I think Tolkien was engaged in creating a measure of purposed inconsistency, especially between sources: the Annals versus Quenta Silmarillion for example, or the variant texts regarding Numenor -- and perhaps even a bit between the long prose versions and the brief chapters of Quenta Silmarillion, or versus the poetic versions. A perfect consistency was not only not necessary, but not intended in any case.
But I'm still not certain why this leads you to post:
'... studying it all from the external fictional, he wrote this stuff in the 1910's-70's is ALSO a way of understanding it - just a limited and to me comparitvely shallow mine to look for jewels and ore,...' This seems to suggest that because of the opinion above, I must be approaching the whole of Tolkien's work in some sort of detatched scholarly manner, 'studying it all from the external fictional' of A to Z, although I'm not sure what you mean by looking for jools and ore if this is the right context.
I don't disagree with what you posted
'on at least one level'
Or do you think I must, or still do, given this post?