"Must be very different indeed.." to me reads a little bit as an insult to our profession, given the context in which it was said.
So I'm a little confused here as to why you don't understand why an unstable patient may go to surgery if you've been an RN and are medically trained (given your username). You have a lot of gaps in your story and I'm not going to try and determine if your vet was right/wrong because it's not my place and I wasn't there. With that being said, common sense tells me that if a dog is already septic due to a limb infection, amputation right away may be the dog's best option for survival. It's not like human surgeons wait until a patient is perfectly stable before performing a life saving operation. Ideally every patient would be perfectly healthy, but then we'd never do anything but spays and neuters. I get having questions after losing a pet like that, but don't be afraid to discuss these questions with your vet instead of not doing that, and still being confused years later. Given that your vet had full knowledge of the case and what happened, you may have gotten some answers and closure.
Also, FWIW, even perfectly healthy animals undergoing elective OE/OHE can code while recovering from anesthesia. I've seen it happen to my own patients despite proper monitoring by machines, myself, and other experienced staff. Sometimes you just cannot get them back, and it sucks. Recovery is the most dangerous part of the anesthetic process. There are many physiologic changes happening at once. I imagine it's the same in humans.
You ask how long the techs I was referring to have been in practice...there are a lot of techs that leave the field within 5 years or so, but there are also a lot of techs that are lifers. IMO vets seem to treat techs better than MDs/DOs treat RNs (or at least from the stories my RN cousins have told). However, these same techs I know would never tell someone at a party 'Oh, just take your dog off this medicine if you don't like the side effect then.' I listened in horror as a family friend (RN) told my mom to just take my grandfather off his BP meds so he wouldn't get another gout attack. I've also seen a ton of RNs offer medical advice on FB, I can't recall a single time an RN told someone to go to a doctor. I'd estimate that a good 90% of the time, I see techs directing people to their vet's office. It just seems that so many RNs out there believe they are more educated/better qualified than a doctor to make those calls and give that advice. I have no doubt than an RN has the intellectual capacity to complete med school, but they didn't complete RN school to be able to diagnose and treat.
Human med seems to have a pretty big issue with class warfare, I just don't think vet met fights that battle to the same degree.