What I have read on the Y cells is deeper cold discharge but no charging change...The winston cells are LiFeYPO4 (A different chemistry). Supposedly it improves the temperature performance of the cells. From their website:
"Winston incorporate Yttrium to enhance the cell temperature flexibility as well as performance overall. "
I have an email out to them asking for more details on their cold temperature limits for Discharge, Charge and Storage. I'll post it here if I get any response.