That is incorrect. Because they are condensed, they are viewed as needing to go quickly and therefore lightly over material. Summer classes are generally perceived by medical admissions as less rigorous than fall/spring classes no matter where they are taken. It is advisable to avoid them if possible
Taking summer preq classes no matter the course load should be avoided
taking a full course load in the summer is not only extremely difficult with the short time, and risks impact to GPA, doing so may be perceived as trying avoid tougher regular term