A mushrooming bullet does not cause this kind of damage, velocity does.
As many of you know when you shoot a small animal with high velocity it blows up. Why? because the bullet mushrooms? I think not.......... no............ I know not!
Two things cannot occupy the same place at the same time. So when a bullet enters the body are likely over 3000fps the tissue is doing everything within the laws of physics to get the heck out of the way. This rush to escape the path of the bullet as the shock wave of energy blasts tissue out of the path of the bullet crushes and rips to bits everything surrounding the path.
This makes things very messy and creates massive destruction and trauma. It would happen with a monolithic solid, or a cup and core, the bullet construction is secondary to the velocity in most cases. Shoot a coyote with 3500fps 100 grain solid from a 25/06 and that coyote will be nearly cut in half, use a 100grain Vmax and the results are not much different.
The reason game seems to explode is that the structural integrity of the hide cannot contain the rapid expansion of the tissue. On bigger game the hide can contain the "explosion" and it seems fine from the outside, but the inside is blended into one big gooey mess!
A 300 WTBY is a very fast cartridge for a 100lb doe. I've seen the exact results on 90-100lb impala from 300 ultra, 300win, 7mm mag, and several other cartrdges of similar speed and bullet weights that my hunters use. I would not rule out the exit hole with a quick once over. I would not be at all surprised to see that there was a hole someplace on that deer and it's probably bore diameter or maybe even less as the bullet squeezed out the the skin and it recovered back to a very tiny little hole. The skin is so elastic that often it will contract right back to a pin hole looking hole rather then a 1" ripped open hole more common with an archery broad head.