Mikkelsen retired last year in Portugal and Sardegna due to engine failures. In both cases, the issue appeared to relate to the car ingesting sand after which it lost a cylinder and misfired. Also, in Sardegna and Portugal Kremer too retired due to engine failures. He also had the Fabia evo.
So perhaps it's just that Škoda doesn't want to risk with the same things happening before they can test it out on drivers who are not gunning for the title.

