Not really, depends on how you set it up though.
If you add O2 inside the the dry section(sealed) and CO2, that can work well as a reactor chamber.

In a plant specific wet dry, the chamber is sealed, the over flow level is 4" or less to the top of the tank's water level.

This minimizes CO2 degasing and O2 exchange and is a bit like a canister filter.

But the added surface area of the sump area increases exchange with O2 in the air from high to low(tank water). That is different than the canister filter.
It's economical for larger tanks and well suited to put other junk out of the tank and into the sump. Also maintains nice surface clarity, no evaporation lines etc.

They are also much much easier to clean.
Most use sponges and/or floss and/or media etc in their canister.
These can be stuffed into slots in a wet dry sump and added/removed with ease and not siphoning issues, bleching, clogged media, taking off the canister top, sloshign water around etc etc

Folks do not clean their cnaisters for too long is most cases.
Wet drys make changing/cleaning media a breeze.
You have a lot more volume for media as well.


Regards,
Tom Barr