Comment by bialpio

One example where picking units within a project is still not saving you from cognitive load is e.g. when doing woodworking. Ymmv, but I can add decimals way faster than I can add 7 9/16" + 13 23/32" (numbers picked arbitrarily but close to a precision of 1mm so if you are ok w/ that precision, you don't even need fractions in SI).