You’re seeing the tail end of a transition period between two competing UI conventions.
Double-click to open a file or folder has been the standard for years (decades?) in virtually all major desktop operating systems.
Both OneDrive and Google Drive are web-based implementations of tasks that traditionally have been desktop-only, which leaves their designers in a bit of a quandary: do you follow the UI convention of the system you’re replacing, to make it more familiar, or do you follow the UI convention of the system you’re replacing it with, to make it more up-to-date?
It’s a tough judgement call with no objectively ‘correct’ answer.
One could try to make the case that a product aimed at a generally younger, web-native audience should go with single-click; or conversely that one designed to closely mimic the traditional File Explorer / Finder UI should go with double-click; but it’s a fuzzy distinction and both of these products are casting a wide net as far as user base so it’s reasonable that Google and OneDrive would have come to opposite conclusions. (Notably, though, as far as I can tell Google stands alone here: other file-sharing apps, such as dropbox or box.com also seem to have gone with the single-click model for their web interfaces.)