Nope, he's wrong. I know he's a vet, but vets can be misguided too. You just need to look at the ingredients to see that they are very different. And the crude fibre content in rabbit pellets varies between 14 and 32%, that's a huge difference.
Of course, there is the argument that if you only feed a little pellets that it shouldn't make too much difference to a healthy bunny with a hay-rich diet, but that still doesn't mean that they are all the same, and I think it's worth paying a little more and doing research to get a decent brand with a high fibre content.
Also, if it's protexin Profibre pellets you're talking about, they're not really the same as normal rabbit pellets, they don't have all the added vitamins in, so I wouldn't recommend replacing normal pellets with them completely unless you have a specific reason to and bunny has a varied diet of greens etc daily to get the vitamins from. They're designed to be more of a supplement. ETA: The crude fibre is 19% and the dietary fibre is 46% - crude fibre is what is measured as fibre in other rabbit foods. I personally think pro-fibre pellets are more beneficial due to the pre and probiotics in them, rather than the fibre content, but probiotics are controversial in rabbit-medicine.