He's not confusing it.

> the price of everything rises by the same proportion

Due to regulation, that's simply not the universal case - e.g. rent control. The economy is conceptual, but prices are concrete leading to some ironic situations.

Inflation is when the currency itself loses market value. There's no such thing as inflation that only affects some goods and not others. The prices of some goods do fluctuate relative to each other, but that's not inflation!