They did, and its too bad.
It's not all bad- the book Uncle Sam's Locomotives by Eugene Huddleston talks about how the USRA Heavy 4-6-2 used the firebox from the Heavy Mikado and the boiler from the Light Mikado. Quite a few post USRA 4-6-2's used the Heavy 4-6-2 boiler with 73" drivers. The book had a nice chart with the useful stats for the USRA locomotives including things like minimum and maximum outside diameter of the boiler. I had a copy, but I can't seem to find it right now, if I do I'll post the relevant info from it.
Bottom line, I'd use the light 4-6-2 to represent engines of USRA descent since the boiler is from a light 2-8-2.
The heavy 4-6-2 is probably more representative of 4-6-2's that were a good bit bigger than the USRA engines.