The butcher's comments sound completely bunk to me. Although there may be some difference in overall taste by not keeping your meat vertical with good air circulation, this variable is often out of our control during hunting, and for a short amount of time right after the kill with a dressed animal, the difference will be small, in my opinion.
Your butcher is probably doing what most deer processors do and is going to take your deer, and 12 others, and process them in bulk. You get back your meat pound-for-pound, but it could be from any of the other 12 animals. This means your meticulous care of your animal goes completely to waste when you get some idiot's deer that was poorly dressed and poorly cared for.
Butchers control for this aggregation a little by trying to reject lower quality animals, and I think that is why they don't want to butcher yours. There may be other factors at play if this a local butcher, such as he is full up and doesn't want to admit it, only wants to process larger animals because his profit is higher, etc.
Your doe could have had the supplest of summer succor to savor, and have meat that is so sweet and tender that it makes the best Waygu beef taste like sawdust in comparison, and the slight delay in hanging may have not produced the apex taste of that meat, but it could still be one of the best deer ever. Or, she could have been subsisting on twigs and bark, and no amount of care will elevate her beyond the grind-and-heavily-spice stage. I wouldn't think twice about how you handled your deer if it were mine, and I would process her expecting the taste to be much more controlled by her summer diet than your handling.
Do yourself a favor and just process the deer yourself if at all possible. The results are so much better than the processor, in my opinion, that the ability to process the animal myself is what has kept me big game hunting after some of the other attraction has faded.
Everything you need to know about butchering a deer can be learned from Youtube and reading, but for deer, I would start by identifying the prime cuts (tenders, and backstrap) and cut those out and save for steaks. Then start cutting high up on the rump. Cut off a bit, fry it up and try it (maybe a dash of salt to bring out the taste). If you like it, cut steaks out of that muscle group. Keep going and soon you will run out of steak. Grind the rest. Cut off bits from different parts and do this sampling technique and quickly you will know what you want for steaks, stew, or grind. Once you do this, you can tell by sight, feel, and smell, even after the meat is off the carcass. Enjoy the best part of deer hunting, in my opinion, the butchering!