You're making the same mistake. If inflation is transient, the price _increase_ is transient, but the high prices remain. It would only go back to 2/gal if the high prices themselves were transient. Which I really hope is the case, but IDK.

“Inflation” means “increase in price levels”. That’s it.

“Inflation is transient” fits prices increasing and then leveling out, and does not imply that every bit of price increase is balanced out one-for-one by immediate deflation afterwards.

As for gas prices, it’s going to depend on supply (including refinery capacity) and demand. The $2/gallon of April 2020 was an artifact of covid nuking demand.

Transient inflation means the $4 / gallon milk prices stick around and don’t go any higher. Going back down to $2 would be deflation.