Yan, thanks for pointing that out.
I think you might be right. I bought two of these tree peonies from a regular plant nursery and they were labeled as Hanakisoi, but their foliage has been this lovely purplish hue the whole time. It seems like having them in full sun increases the purple color to the leaves. There also was no sweet smell that a Hanakisoi should have, but I thought that was on account of it being a young plant. Is Yachiyo Tsubachi the only pink flowering tree peony with leaves that stay this color all summer?
This is the same plant a few days later in the full sun. The sun really wreaks havoc on the bloom, I meant to move it to a shady location for viewing sooner.