Me too have never heard of Polish breeders having Bask progenitors in their breeding programs complaining about their characters. On the contrary, they are proud of their successes in the showring and under saddle. I'm sure there are some exceptions as in every sireline, but I've really never heard of them in Poland. Generally Kuhailan haifi sireline has better reputation in my country than Krzyzyk sireline.
I have a lot of Bask in my breeding program, in both the stallion and the mares. They have been beautiful halter horses with great pleasing personalities that go on to successful show careers. My foals are slower to mature than some, but generally worth waiting for and get better every year. I think my stallion is more beautiful today (in his teens)then he was as a four-five year old.
Coming back to Bask: Mr Pankiewicz remembers Bask as a horse of a very good and gentle character. He was his favorite horse while in Poland. Mr Zenon Lipowicz, who was riding Bask, when Bask was in training at Sluzewiec Race Track, tells:" Riding Bask was pleasure and relaxation. He was obiedient, brave and cool-headed. He had great motion: soft and elastic like arabian and with like fullblood long steps, with constant speed on the whole distans without additional dispositions."
I've heard about Polish horses slow maturing too. It's one of Polish horses atributes, but hopefully it isn't a fault.