Nope, they're right, an enzymatic cleaner breaks down the actual molecules that cause the odor, rather than just covering it up with perfumes (cats can then still smell the ammonia underneath). Nature's Miracle is probably the best known and most widely available one, so you don't have to get whatever your vet is selling if you think it's pricey.
"To close your eyes will not ease another's pain." ~ Chinese Proverb
“We must not refuse to see with our eyes what they must endure with their bodies.” ~ Gretchen Wyler