Absolutely nothing wrong with a crank turned past .020.
I am amazed at all the wives tales. The same guys that spread this stuff will read about small journal or Honda rods on a steel crank in a magazine article and think its the hot setup.. What is the difference?? The crank can be used for any journal size. If it is nitrided so what? Any regrind past .010 will usually remove/compromise the hardness. The crank is still usable if it is grindable.
SBC cranks (large journal) can be ground to any of these available sizes..-.010 .020 .030 .040. .050, .060, then to small journal std. -.010 .020 .030 .040 .060 I have all these sizes in stock most of the time. Plus in performance bearings + - .001-.003 increments are available in many undersizes. Then they can be turned to Honda rod journals std. plus several metric undersizes..Just have to watch where the oil hole ends up.
Many of these combos are used in racing. Several of my customers take a new GM steel crank and have the rods off set ground to small journal size, to gain a bit of stroke and reduce deck height. Same with 400 iron cranks.
Back in the day we did 350 cranks, cast and steel, with off set small journals all the time. TRW even had off the shelf pistons for the combo.