The article didn’t make that conflation at all. The author, a former professor of mine in law school, knows what he’s talking about (as do I). It was the commenter who was confused (as are you).

Jurisdiction has nothing to do with whether laws are applicable to a case. It has to do with whether a particular court can hear a case. Personal jurisdiction questions go back hundreds of years to resolve issues like “is it just to force a defendant to travel hundreds of miles by horse and carriage to defend himself?” versus allowing him to defend himself closer to home.

If the plaintiff sued Shopify in New York, this issue wouldn't have come up at all. (And, yes, a New York court can apply California law.)

This stuff is all covered in first-year civil procedure in law school.