As Callum well knows, relates to Package Manager Update grasshopper conflict - Rhino Developer - McNeel Forum and other threads.
It’s not clear to me why package manager needs to retain old package versions. If it’s necessary for some plugins, it would be good if packages could opt out of having old versions retained using the manifest. From the outside, it seems that downloading is easy and practical for upgrading, why is it not the case for downgrading? I’m assuming McNeel keep statistics on this, is it common for users to downgrade plugins?