Does a camera dictionary work without an internet connection?
It depends entirely on where the dictionary lives. Apps that send the recognised word to a server need a connection for every lookup; apps that bundle the dictionary work anywhere. The download size gives it away — a full English dictionary is well over a hundred megabytes, so a 30 MB app is almost certainly calling out to something.
Text recognition itself is usually on-device on modern iPhones and is not the constraint. The constraint is the dictionary data.
Booktionary bundles both: 156 MB of English and 189 MB of French, which is 94% of its download size. That makes it a large app, deliberately, in exchange for working in airplane mode, on the underground, on a plane and in places with no signal. Nothing is sent anywhere, because there is nowhere to send it.
The side effect is privacy: with no network calls there is no account, no history and no analytics. The App Store privacy label reads Data Not Collected.