I find it hard to imagine that systems which store "PST" and rely on a hard-coded assumption that it is -0800 would be robust to normal changes in time zone rul

I find it hard to imagine that systems which store "PST" and rely on a hard-coded assumption that it is -0800 would be robust to normal changes in time zone rules, which already happen regularly. Like surely those systems would have already broken in 2007 when the rules of America/Los_Angeles changed such that the date of the yearly transition between PST and PDT changed.