My first experience with tissue culture peonies was 7 years ago from Peonies Plus. I had no clue what I was ordering and was aghast when I saw the tiny roots. Also made the mistake of getting them in the spring and didn't baby them along, half didn't survive the transplant. It took 4 years or so for the first blooms, just divided the 3 that made it last fall for the first time, just split them in half to make a trade for a couple of Itohs that I didn't have yet. Can tell you from that experience that those tissue culture roots do eventually grow into the woody monstrosity that you see with any other Itoh division!
Ordered what was clearly marked on their site as bareroot divisions from Peonies Plus last fall, those were pretty massive roots. Definitely pays to actually read the info provided about the roots offered!