While your vet did get some things 'wrong', or at least contradict them to what common practice is... The vet isn't entirely off the ball. For a pet animal that is also going to be a display creature, a larger enclosure isn't a bad thing...provided, of course, that there are many hides, and if the enclosure is really that large, multiple water bowls and heat sources, and so on and so forth.
Yes, we do overfeed our snakes...but we do it on purpose for breeding. It's not a bad thing to only feed your ball python one meal every two weeks...granted that that meal is appropriately sized. It's probably better for them not to eat so often, especially if they're not going to be breeding. My adult males only get fed every 14 days, maybe every 10 if they're looking hungry.
If you read up on husbandry practices in other countries, ball pythons are often kept in cages with climbing furniture, basking lights, and even UVB lights...granted, the snakes don't need the lights for calcium absorption, but they do look pretty darn awesome displayed under them. The goal is not to just keep them, but to give them lots of choices, and for the snakes to pick what they like best. It is an interesting difference in perspective. The books I have read were published in germany, and the authors still used UTHs underneath a couple hides in their enclosures.
The problem that I can see with what your vet was telling you was that she/he was describing the care for ball pythons if you want to go the step up from the basics. Large, lighted enclosures are all well and good for someone who knows what problems they will run into, and can counter them, but the average beginner is going to have a hard time keeping the snake thriving in that kind of cage.
So maybe that's a tactic you can take - mention that while what she's/he's describing may be what's "best" for the snake, the average or beginner keeper usually doesn't have the knowledge or experience to be able to cope with keeping a snake in a cage like that.
Disclaimer - I keep all my snakes in plastic boxes because I will admit I can't keep them thriving in a large, pretty display cage. 
~jenny
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"Polysyllabism in no way insures that what you're saying is actually worth being heard." - Blake (an e-friend of mine)
"I have never made but one prayer to god, a very short one: "O lord, make my enemies ridiculous." And he granted it." - Voltaire