[juki]

Chinamax means ships that can use specific harbours, which imposes a length limit. Panamax likewise has a length limit because the ship has to fit inside the locks in the Panama Canal.

The Suez Canal doesn't have locks, so in principle the length isn't limited. In reality it of course is limited by the harbours you intend to use. Apparently ships longer than 400m also require permission from the Suez Canal Authority.

More important for the claim that Chinamax is bigger is the tonnage. Chinamax can carry 400,000 tonnes, while Suezmax is typically under 200,000 tonnes.