Janis might be right, that sometimes wrong seeds are included in a seed exchange.
But it must not be done with bad faith of the donors:
I remember that I noticed the seeds of speciosus (bright red) and speciosus
Albus (brownish-red) look totally different, same with Crocus chrysanthus
(bright red) and chrysanthus Afyon (dark red) - sorry, I don't have photos.
Later I have learnt from Helmut Kerndorff, that the seeds are also a valuable
feature to distinguish different species.
Meanwhile it has turned out, that the Turkish 'ex'chrysanthus plants really are different
species, and I think, that the plants in trade sold as speciosus Albus (from the Caucasus)
could also be another species....