What would they diagnose?
Combustion Engine? Don't have one. Transmission? Don't have one. Emission Control System? Don't have emissions. Spark Plugs? Nope. Fuel System? No. Exhaust? No. Alternator? No. Battery charger? you can see that on the dashboard. Starter motor? Nope. Battery Status? Also on the dashboard. Vehicle speed... on the dash. Engine idle... no. Air Flow Sensor? No air flow. Intake Manifold Pressure... no intake. Throttle position... only really relevant if you have a clutch or torque converter which EVs don't have (you would notice, very quickly, if the throttle position detected pressing the pedal when you're not pressing it in an EV...
That's the list of standard ODB-II diagnostics. Some cars do more than that, but those are the ones they have to do. And none of them are relevant.