Drip brew ratios allow for the fact that some liquid will be retained in the bed, so you don’t need to add additional water unless you’re aiming for bizarrely tight tolerances in concentration (I don’t know why anyone would do this).
Different brewers & even different grind settings in the same brewer, can change the amount of retained liquid, but even if the beverage weight varies across brewers, they are all still the “true brew”. You might see +/-0.05% difference in concentration at the same extraction, which isn’t much. I guess you could brew at say 58g/L for Melitta & Kalita brewers, then 62g/L for bigger Chemex brews to compensate, if you really wanted.
I tend to use a brew stand on scales for smaller drip brews, then I have the cup on a second set of scales on the brew stand. This means that for a given recipe I can ensure a consistent beverage weight out, relative to the water added. If I keep the brew water to +/-1g then I can keep the beverage to +/-2g easily enough. If you have a cup/server of a known weight (e.g. my Chemex is 586g), you can also weigh this at end of brew, after dumping filter & grounds, & deduct vessel weight
Always let the brewer drip out for a little while after the brew appears to have ended, this will help consistency from cup to cup. If you’re pulling the brewer with +/-5g in the cup for 200g average brew then that’s a 1% extraction span, even if you get everything else perfectly consistent…which you won’t.