I thought the purpose of this exercise was more about getting the left hand to move quickly and accurately and the pick/strum/pick exercise was about playing the chord correctly but I've read different opinions on this.
Your correct in you assumption but and this is a big but. "Practice Makes Permanent"
If you ever want to make quick chord changes practicing sloppy changes will make
you very good at fast sloppy changes.
If you want to make quick clean changes you must practice clean changes.
I'm not a big fan of the OMC exercise. To many people start doing it way to soon and
put way to much focus on speed. You must first be able to play the chords correctly
before you can become fast at changing between them.
I personally think your better off learning song and getting your chord changes up to
tempo. There are very few beginner song that need more than 1 chord changes per barre
and at 120 bpm that 30 changes a minute.