I've moderately familiar with this plant, and your advice is quite sound...
Incidentally, before I dirty Don Schnell's name with rumours of S.
oreophila and S. purpurea mix-ups, note that this sort of thing can just
happen to the best of us! All you need is a less than perfect situation
and a rogue pollinator (even wind) could screw things up. Also, it
might have happened at the seed bank. Also, possibly a seed from one of
my pots might have gotten into another pot (water splashes?).
Some of my D. falconeri are trying to flower. I nipped those in the bud
pronto. Also on the petiolaris front. I planted my
falconeri/lanata/petiolaris plants in peat, peat/sand, or peat/perlite.
Some are doing much better than others, but it is NOT correlated with
soil mix. I.E. 1 falconeri in peat/sand is doing well, but of the two
in pure peat one is doing great, the other poorly. So I don't think
soil mix is too important yet. At least for my growing conditions.
BAMR