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