I can't really argue with your quibble. I ain't saying it's right, but people do it. At $35 for a complete analysis, it really isn't saving you money either. I did one just for fun and found out the Mobil 1 Delvac I was using was just about worn out at around 8000 miles. Mind you this is the oil that long haul truckers use for around 50,000 miles. A case of 4 gallons cost me around $120 too!
Needless to say, I have had a change of heart once the Delvac runs out. I will update my post with a "warning".