Ok so going off that page, everything down as far as Slow West is still in stock. The likes of Ida, Still Alice, Rudderless etc. had been on the international store since release & could, potentially, have just sold out. Or the pandemic hit &, because these items weren’t selling internationally, PA just decided to move all stock to the Korean store.
I’m not sure what the issue is, Plain Archive have always been very clear that there’s a certain allotment for the international market & a certain allotment held back for the Korean only market. Which is completely fine. There’s plenty of companies that don’t ship internationally at all. Shout Factory, Criterion, hell even HMV don’t sell outside the UK. The only difference is that these were available for a while & now aren’t.