I read it as both, but UK suppliers have stock of various SATA HDDs available in large and small sizes. It's hard to say if prices will rocket or availability decline, or both. I don't normally advocate panic-buying, but if it's needed now is the time. I have one NAS spare on hand, I don't want or need a drawer full of them, but it'll be a royal pain if I do and can't get parts.

Lower performance/capacity consumer drives might be comparatively safe because there's Chinese end-to-end production capacity for those. Of course the price can still increase, but probably not that much.