Update: went back to that field on Sunday and the blooms are much more a "normal" small. Iow - they are small but within acceptable range for a young plant's blooms.
I think I just needed to give the plant a bit more time for the flowers to develop!
Liz and Lynn - I hear your point on the cold. Our cool wet spring has definitely affected bloom size, count and even color in some varieties!
That said, SitR is on the warmest part of our "second" farm (zone 5b/6a not 4b like our main farm) in a bed that's almost too well drained. Suspect the size issue comes down to 1) youngish plant and 2) my cussed impatience! The plant is vigorous so will likely divide as planned.
Liz - Agree on TC. Obviously, we'll always field grow any peonies we propagate/sell and we usually source from field growers only. But honestly, if one of our itohs started its life as a TC, then so be it.