Scale technician by trade. Does it matter? I don't know. Given all the "uncertainties" in weighing masses, there's a lot of variables that can work against you each and every time you pull that trigger. Things like the electronics in the scale (were they Chinese made or American? / and who has the best?), the tolerances of the weights that were used to calibrate the scale (did you use Class 1 or Class F? / were they certified by a state entity?), external factors (were you in a controlled temperature environment or were you in your shed with high temps/humidity?). All of these contribute to what we call "uncertainties" in weighing.
Did the bullets all weigh the same? Did the cases have the same internal capacity. Were the primers the same lot? What kind of scales does the manufacturer's of the bullets, the primers and powder use? Are they calibrated daily, weekly, monthly, quarterly, semi-annually or annually? Did the technician give a crap that day? Was he sufficiently trained? There are a lot of unknowns before we ever put the cartridge together.
Then we take them to a different environment (outside) and plug them into a rifle that was probably made or assembled by a person you don't know (mass production) or to the most you are semi-familiar with (your gunsmith) and only because you send him/her large quantities or your hard earned money.
And then we pull the trigger.......and hope (more likely assume) we hit the target. In a 1000yd laboratory this would be a cinch, kinda', but now we're dealing with temperature, relative humidity, the WIND (speed, direction, consistency) the spin drift of the bullet and the Coriolis effect (are you shooting in the Northern or Southern Hemisphere? are you shooting toward the East or West? North or South? do you know? do you care?) Does your ballistic app take all this into consideration?
Should we have to worry about all this? I don't think so. As humans and a society, we usually choose and pick what matters to us most. We do it with the Bible, our partners, our children and our jobs or businesses and hobbies.
Now that the somewhat pessimistic ranting is out of the way (which I'm not) I will say I weigh each of my charges on a RCBS Charge Master at .2gn less than my desired target weight. Then I moved it over to my other scale, a Mettler Toldeo AB104-S and use the Omega powder trickler to finish it off. This unit reads out to .002 (thousandths) of a grain and my tolerance for most of my loads is +/- .004gn. This set up gives me confidence in my loads and that they are the best that I can assemble each time, but I shoot mostly factory rifles for long range targets and hunting. The one exception is a Kirby Allen built .270 Allen Magnum, which has a voracious appetite for slow burning ball powder. So far I have only used US869, which I don't think is temperature insensitive but it shoots absolutely great past 1000yds, regardless of all that we have to put up with!