I can say without question Apple sucks balls. I will never buy their products and be linked to their proprietary hell. I am working developing apps for Android and Apple at this moment. Apple is a complete and utter pain in the rump to use in general. They might change their mind but I doubt it. Why not call your app something else like make is sound scientific for formulation calculations. It is the same thing and you could get it past them. Just omit all the nic and juice talk and keep it down to real science. But then I guess if you did that people that actually knew science wouldn't need an app at all.
I think what most people need seems to be a basic math class! These are not complex calculations folks. If you use weight it is truly so very easy. Note your weights precisely, taste and if you hit the taste it is simply a matter of a multiplier to scale it up. I realize my background lends itself to understanding how simple it is with a pencil and paper and calculator if needed. Just seems like basic school math should cover most people on this forum for how to do these calculations by hand and then scale them up.
CC
The trouble with that is there are so many students graduating the public school system these days that cant even make change unless the cash register tells them exactly what the number is. Many kids these days know nothing of using their grey matter or a pencil & paper to work out the answer, because they were taught how to do most of their math using calculators instead of their brains.