I would argue the premier of BC is a fairly powerful position. Especially since, regionally, the NDP or Liberal party have been in contention for BC since the early 90s- over 30 years.

I would say that duverger's is "true-ish" but it doesn't capture the correct mechanism and fails on a predictive level enough that it at least should not be called a "law".

Its almost certainly suggests what's going on has more to do with voters gamifying their elections rather than any tendency of the elections or parties themselves as canada shows you have people voting liberal for country level government and NDP for regional seats.

A true successor to Duverger's Law would state that ftpt has a tendency to cause voters to vote strategically among the two most dominant parties in any fptp election. This would be more in line with what we actually see.