In my opinion, due to such possibility of the use of plant growth regulators such as Colchicine, GA3 and a host of others used in commercial nursery applications, the results of the study although interesting, may not hold as true if the Byblis study material had been harvested from the known Byblis populations in the wild.
This would possibly be true if the article only dealt with chromosome numbers. But you are ignoring the fact that they also looked at the position
of the 5S & 45S ribossomal RNA gene arrays as well as actually sequencing DNA - and not a single gene but the 5S-NTS, ITS (both nuclear), rbcL, and trnK intron (both chloroplast).
The species are thus very well supported by different data sets: chromosome numbers, gene positions, and DNA sequence. Not to mention taxonomy, ecology, geography, and all that we already knew. Hard to get any better than that...
Considering that the authors are Japanese, I guess we can assume that the plants used in the study came from Isao Takai.