Most pheno's have shown sex roughly between day 20 to day 30 I have heard of a few going just over 30 days before showing pre flower but nothing this long before. This is definitely an odd ball phenotype. Could have possibly even been a semi auto phenotype possibly which can randomly show up at any point in a breeding project. These are out of the S2's which are pretty much the same as a F3 which is fairly well into the breeding project. I had gotten the original beans from Tony Greenhand as auto beans about 3 years ago as testers so Im not sure at what stage they were into his breeding program when I gotten the original beans.
Yes most of the phenotypes will show dark purple stems once flowering has induced and some phenotypes will put out dark purple leaves and purple flowers without introducing cold late in flower.