Originally Posted by Bobby_M
Nit picking but mash efficiency is a measure of conversion and diffusion, i.e. taking a gravity sample directly out of the mash and using the total water addition as the dilution figure. This is a measure of how much sugar you got into the mash wort.
Ha! Nit pick accepted.
I would think a potential issue with this approach is that water to grist ratio would have a significant impact on the "measured" result vs the actual result. Less so, the moisture content of the grain, but those would both impact the percentage of water absorbed in the grain. Not saying it might not be a useful number, particularly if using the same grain bill and water:grist ratio over consecutive batches.