Are your comments based on measuring efficiency at the end of the process (based on gravity points at the end of the boil) or based on gravity points preboil?
Those would be the same. Sugars aren't created or destroyed in the boil, only concentrated.
I understand that.
But some people measure efficiency by the volume that makes it into the fermenter. So basically points that make it to the fermenter divided by theoretical points in the grain bill.
But that measure of efficiency doesn't do me much good, because I lose wort to different things at different volumes depending on the beer I'm brewing. For example, a heavily hopped IPA will have worse efficiency than something like a simple wheat ale because I'm going to lose a ton more wort soaked up in hops.
I prefer to measure the efficiency out of the mash, and from there I can calculate my recipes because I account for all those other losses in my spreadsheet by increasing the volume of wort required preboil.
My mash efficiency remains fairly constant near 75%. It does vary a little because my mashtun loss is constant, yet my preboil wort volume varies by recipe as described above. Recipes that require less wort will show a slightly lower efficiency preboil, because that mashtun loss is a greater percentage of the collected wort.
I should tweak my spreadsheet to account for that, and I'm sure the efficiency would hardly move much at all unless I changed my crush or something.