I think the point is that if you store local time, and have a decently maintained time zone handling library, the library will adjust correctly for before/after

I think the point is that if you store local time, and have a decently maintained time zone handling library, the library will adjust correctly for before/after the switch, but only if you store in the local time. Of course it can't happen by magic, and you rely on the authors of the timezone libraries (a thankless task in itself), but if you remove a dimension of your data, nobody can ever help you.