Except the discussion in question isn't about looking at raw HPS value, but more about WHM being able to outperform SCH in both the HPS and DPS metric at the same time. Of course it stands to reason that a healer who heals more will be DPSing less but the question still remains if a WHM who is HPSing more will still output more DPS than a SCH who has to perform at the same percentile of healing as a WHM. That's something you can infer by digging deep into the bowels of the site which shall not be named.
Or to put bluntly, if both WHM and SCH need to output 6,000HPS to succeed in the fight; how much DPS will they still be outputting by the time the fight is done and how comparable are they? You'll need a lot of datapoints to answer that question but it's definitely more than just looking for raw HPS values that is implied in your post.
