"Why is it unreasonable to say there are aspects of God which can't be explained?" Because any aspect of God that has any effect on the natural world in which we live, MUST have been done in a NATURAL way. True SUPERNATURAL cannot interact with NATURAL or else it becomes NATURAL. Once it is in the realm of the natural then science can jump all over it, poke it, prod it, disect it, reverse engineer it till we know how it was done. I contend that whenever God interacted with our universe he would have done it according to the physical laws which He put in place.
What if God changed the laws of nature, worked a miracle, and then changed them back to what they had been before? Then there would be no way to examine that miracle scientifically. Either you believe it happened or you don't.
Any theological or quasi-logical mind-bending still doesn't make God's existence any more likely. It just shows that it might not be impossible - outside of anything scientifically observable.