It's not just weight--it's water, amount of water, mash temp, pH--there are many things that make the same recipe produce different outcomes.
And from a bittering perspective, I don't think it's news that people should adjust hops for alpha acids.
On a homebrew front--and especially for newbies for whom there are already a lot of variables to consider--one can go too far with this efficiency approach. It's a more advanced element of brewing, and certainly something with which those brewing for profit must concern themselves, but for the rest, is it all that important? Probably not so much.
I just brewed a hazy IPA with a codged-together recipe based on something I found online, trying to clone Sierra Nevada's Hazy Little Thing. I changed the malt bill (added some Maris Otter where the original said only 2-row), and the hop bill is different due to lack of availability here as well as personal taste (I don't care for Mosaic hops much, cut down the proportion by 50 percent). But I still expect the beer to turn out, and be good, even though it might not perfectly match the flavor expectations I have for it.
If repeatability is the goal, then some of the measurement things are important. But at my local level, I *can* repeat. It's the portability of a recipe that's the issue, IMO, given differences in malt, hop availability, AA%, water, etc. etc.
If this IPA turns out, I'll probably post the recipe, with my caveats.