Hardened valve seats - do they really matter?

Yup I put a '77 peanut plug head on a 74 short block and before a 0.070 mill had 60cc chambers. After I had 1at 48, 1 at 49 and 1 at 50cc
I had the machine shop CC it and it came out at 60. I was driving when I got the call and did a quick off the top of my head guess when I told him I wanted 70-thou off.
Had I known my pistons were still 0.180 in the hole after a 0.030 block shave i'd have had them do a deeper block shave.
I wonder how much +/- tolerance they had for block deck height and/or head thickness after they were cast and before assembly on the line and how many were actually spot checked on that line when they were new
You couldda zero decked that block and it would have never known it.