At a certain point you run into physical realities of living, growing things. You can use ratios to make homogenized items (mashed potatoes or sauces or caramelized onions or sausage). But even if you had two chicken breasts of the same mass they'll need different amounts of sauce or coating since they'll have different surface areas, and different cook times since they'll have different volumes.

I think any recipe for roasted vegetables has to be by volume of the chop/dice fwiw. There's lots of ways to chop carrots into 20g chunks, but they won't all cook well or evenly, so a 1/4" dice is what you'd call for (even if you call for 600g of carrots)

One problem with cooking is that your pans and heat transfer do not scale. So you cannot just arbitrarily scale up/down recipes, even if you take precise measurements. The result may be way too watery or dry, for example.

(I guess this would also apply to baking anyway.)

Why water/water+flour and not water/water+flour+salt+starter? Because water:flour is the key relationship - that's what dictates the outcome. I think some people who do a lot of enriched doughs will give everything as a percentage of the mass of flour, pretty convenient.

Really it's _just_ the ratio, normalized to 100 for convenience

While I agree it is unintuitive, it is super practical when calculating the recipe.

Making a 80% hydration pizza dough? Just measure how much flour you added and multiply by 0.8!

Serious American bakers mostly use Diamond brand kosher salt. Serious bakers universally will specify if they're using kosher or table or some other salt, because they pack differently and provide different effects.

You're going to be much closer following mass measurements than volume ones - your flour may have different moisture and protein levels than the author's. But those are minor compared to the >25% variations in flour when measured by volume.