It does still need CE certification and emissions testing. I’m guessing they didn’t do that and it will be fine because they only sold 2,500 units.

Technically it doesn't - it just needs to be compliant.

It is completely left up to you how you are going to demonstrate this if they ever come asking for the paperwork proving this. This can be a certification by an independent testing lab, documentation from in-house tests, or perhaps even documentation proving that it is compliant by design.