I just had look for that Milne paper and couldn't find it. It must date to around 1930, before Milne took off into developing his own cosmology. I may have a xerox of H.G. Forder's copy.

Milne was a Christian and I'd guess he inspired some later investigations into the relationship between theology and cosmology (e.g. Thomas Torrance). If you have no concept of global simultaneity you don't get to say "when" the Incarnation happened for the whole universe.