In the lab I work in, we convert all measurements to the metric system right before extraction if the biomass didn’t already come in that way. Why anyone still insists on using the (not so) “standard” system is beyond me. For me, it helps to not use it past intake. The conversion, however, can happen anywhere without ill effect. Getting people in the habbit of doing it earlier in their processes may also be of benefit, as calculations tend to be easier (or at least make your job a bit easier).
Our oil can vary in weight but most always weighs just over 1 g/ml for crude (up to about 1.1). When mixed into MCT, it almost always weighs out to exactly 0.955 g/ml (the listed weight for MCT). Almond oil, grapeseed oil, vegetable oil, etc all have different weights, as do cannabis oils. We do all of our formulations by weight, and it has been my experience that while oils tend to weigh close to the same, those small differences matter. Generalizations are fine for most of the world, but I need for greater precision in my lab.
Hope that helps and doesn’t make me look as much of an ass as I feel writing it out and reading it to myself.