Sure, it's not a "Package Manager" by JavaScript nomenclature, where apparently the package manager refers only to the client side piece. Instead it's apparently a "Package Manager" and a "Package Registry"… which most other environments just call a "package manager". As a non-JavaScript developer, drawing this distinction feels incredibly silly to me…
pnpm lets you download packages to your computer -- a "manager", if you will. JSR gives you a centralized place to find packages at -- a "registry", if you will. We use different words because these two things are not interchangeable and it's not just a JS thing.