No , not correct, here in Golden we sync with AB all year in MST.  Fort st John is an other matter. and Creston .

"The boundary between Pacific and Mountain Time Zones wanders down the spine of the Purcells, splitting the East and West Kootenays into two time zones, except for Creston, which marches to West Kootenay time in the summer and East Kootenay time in the winter. Missed appointments and meetings are common.