Yes that is poor QC on that part. Its very close but the oring groove is not breached as far as I can tell. I would clean it up, flush the system, and run it with fresh good coolant. I never ride my new bikes with the factory coolant, and I have seen traces of contamination when removing the cap. To me this is no problem as I assume its just oil/grease traces from assembly. I think that if this were really leaking, your cooling system would be pressurized with combustion gas and appear to boil over very quickly.
Oh, your English is fine and better than my German, which consists of several old drinking songs taught me by a few German engineers when I worked for a TUV office here in the USA.