Apologies, you're right I should have been clearer. I meant he didn't appear on record as a soloist until then (relatively late when compared to someone like James P. Johnson). He did record "Fingerbuster" as a solo in 1934, but it wasn't released until later.
The "Cubs" small band sessions are indeed wonderful. For anyone looking for a digital release of them, I would recommend this one on Timeless Historical over the Chronogical Classics. It was restored and mastered by John R.T. Davies, which is always a good sign. As for vinyl, I would be interested in hearing how the Ace of Hearts sounds.