You are confusing two things. A time zone (e.g. Europe/London) is a geographical region of places always sharing the same time and it does not change at a given location unless time zones come and go. The zone time (e.g. GMT or BST) on the other hand is the time in use in a given time zone at a given point in time and it commonly changes twice a year between normal time and daylight saving time and back. In short, daylight saving time affects the zone time, not the time zone.

You are right. I have heard that one before too. That one is sort of implicitly covered by this part in the blog post:

"CST is also used for: Cuba Summer Time, China Time, Central Standard Time (Australia). PST is used for Pakistan Standard Time and Pacific Standard Time. If you want a unique identifier for the time zone in the Pacific West of the USA it looks like this: “America/Los_Angeles”."

In this case the name of the time zone "people live in" is "Europe/London", not GMT.

The way I get around this in my head is that UK's timezone is "Europe/London". (my definition of "timezone" is "IANA timezone", so while "UTC" or "GMT" are both valid, they aren't what the UK uses.) The "GMT" or "BST" is just a locale-ish thing that gets tacked on to output, much like "EST" or "EDT" for "America/New_York".

But, as the Wikipedia page says "the term GMT should not be used for precise purposes" as it has been superseded by various other standards (e.g. UTC, UT1)

I've encountered English people who made a fuss about the loss of "God's Magnificent Time", but for better or worse GMT is no longer the official name.