To be fair, the common usage in Canada even during the summer isn't necessarily to use xDT to denote the time zone. The average person often doesn't know when DST turns on or off so just uses xST year-round. It's quite common for someone to say "5pm EST" in the middle of July while intending UTC-4 (albeit imprecise and inaccurate). Others get around this by simply using xT year-round.
This seems more like a conscious effort to get more people to actually start calling daylight time xDT, which is currently uncommon. Displaying a time in both xST and xDT during the winter seems to be very uncommon and likely to cause even more confusion (e.g. 3 p.m. PST, 4 p.m. PDT, 4 p.m. MST). Framing this like it is the current practice seems odd as most people do not think about the second letter in the abbreviation. With the exception of BC's Pacific Time which is genuinely challenging, using the official "Alberta Time" and "Manitoba Standard Time" would probably be more unambiguous and intuitive to the average person.
