The picture above is not wet vented.
Wet venting must be fixtures on the same floor and the pipe size is increased one size.
Neither of these two things are happening here.
The lower sink must have a vent run to the upper floor, where it can be revented above the shower or tub,
Or it must have an AAV valve on the trap arm.
Something like a Studor vent.
I also do not see that the toilet is vented.
Fixtures that "are" wet vented would look like the drawing below.