You do raise a great question. The problem with this is what if you put the tube down towards the bottom & still end up pickup up extra's?. The other is are they taking into account the process of counting, I count anywhere from 10-20 seconds, while the initial oil debris flows out of the sump first before taking a sample? I'm not sure a blanket statement like that is the case in every situation or that there are not other methods that work just as well. Wouldn't draining a huge chunk of your sump then sample in the stream be just as good? Just thinking out loud.
I don't have the answers BUT I would assume that consistency is more important. I let the sump, depending on the size, drain for 10-20 seconds then take the sample. If I do that every time then the results should be relatively consistent I would think. Throw in the fact that the tubed kits (kits that come w/a tube) can be more expensive to buy. If you can afford that & the pump then I don't think it would hurt anything.
If going with a tube my recommendation would be to:
- measure the dipstick length (don't include the handle knob)
- put a marker line on the tube with that length
- Get a new hose every time you sample
That should prevent the tube from scraping across the bottom of the pan. I still think getting a fumoto valve & placing the sample bottle after a short bit is the best method b/c it's the cheapest. As long as your consistent then there should be no "Variation".