It has been that way in the past, yes.
Explaining "how can this be" would entail a complete explanation of the purposes of scaling and what it is based on... this has already been detailed numerous times in other threads (which you can refer to for more information). Suffice to say that 'course difficulty' has nothing to do with scaling, and the scaling factors are instead determined by the ability of the course candidature - ME1 has, in the past, had a 'more able' candidature than EE2.
Remember that the scaling for extension courses is determined by the performance of the extension students on the common lower-level paper.