AIUI, it seems that Daniel Ingram has cautiously endorsed the work of well-known Christian mystic Bernadette Roberts as potentially a useful take on stream entry/enlightenment and related things from a theistic, and specifically Christian tradition.

(I'd like to stress the point that no matter what one's stance on the basic question of theism - which to be fair, is only ever referenced very obliquely by Buddhism, with very obscure paraphrases such as "Buddha-Nature"; perhaps out of wishing to avert conflation with the much more clearly theistic-leaning Hinduist tradition - it's clear enough to me that such a well established tradition as Christian contemplative prayer has to be doing something useful for its practitioners, and it makes sense to ask ourselves what might be happening there, and how it might work at a basic level!)

Fairly extensive sections of the Tipitaka deal with the existence and nature of superhuman beings and attribute Hindu explicitly theist beliefs to encounters with them. I don't think it's true that Buddhism only ever references it very obliquely or that it conflates deities with the Buddha-nature. But my understanding is very limited, so you could be right.

I think it's true that Christian contemplative prayer does something useful for its practitioners, but not for the reason you give. Your argument rests on a flawed premise: minimally, that any tradition at least as well established as Christian contemplative prayer does something useful for its practitioners. Traditions better established include alcoholism, contracting sexually transmitted diseases, and death. Your argument would prove that all three of these traditions also do something useful for their practitioners, but I think almost everyone would disagree with regard to at least one of them.