Why would the VA push back my surgery by roughly half a year?

Did they tell you they'd likely get to you during Jan/Feb back in August, or did they just tell you that (which means they will get to you in 2-3 months)? Could be many reasons. They want you to have adequate recovery time from your first surgery. It could be that they have a backlog that is causing delays. It could be that they are short surgeons and/or OR staff. Without being an insider within the surgery department, and/or knowing your medical history, nobody here can definitively answer your question.

With regards to them not "covering it", VA Healthcare is NOT insurance. Unless and until they set you up with community care for your surgery, they have no obligation to cover it.

You should be authorized to get a referral out to the civilian network, but you probably have to ask VA to approve it.