I don't know exactly what to make of this except that this seems to be a function of the drug test itself
Youre right in your deduction. It is due to the function of the kit. The kits utilize enzyme-based reagents for the reactionary process and the amount of enzymes do vary from kit to kit. Thats the main reason why one kit can produce a lighter (or bolder) line than another kit using the same aliquot.

And, by using the same aliquot, it also reinforces the idea that line intensity is not proportionate to the amount of THCA that is present in the urine, despite popular belief.
Burnt Toast Reviewed by Burnt Toast on . Observation about faint lines Below is a picture of two tests I took this morning from the same sample of urine. The two drug lines are of noticeably different intensities (It may not be completely evident from the picture, but they were different). Today also marks 30 days of testing clean (51 days sober). My u/a is coming up next Monday, 8/13 so I've been testing myself every morning for the past two weeks just to make sure I'm good (I'm addicted to testing myself for pot - literally!). I don't know exactly what to make Rating: 5