"not wasting personal calories to warm me and my sleeping bag..."
A lot of people are happy with this so I just let it go, but
when you go to bed, your metabolism is higher so you quickly warm up your sleeping bag
the problem is at the end of the night when your metabolism has slowed down
I suppose if you went to bed really cold, it would tap into your reserves to warm up so you'de have less at the end of the night. Or if you were treating someone with hypothermia, then definitely warm bottles would be good.
But in normal conditions, if your sleeping system isn't quite warm enough for conditions, warm bottle won't make much difference
I normally go to bed a bit warm and leave sleeping bag open a bit and close up when I start to get cold. If I had a warm bottle, I'de just delay closing up a little.