Just the core plugins, and I don’t intend to use any community plugins; but thanks, I’ll check it out!
I’m in the sandbox on Obsidian 1.8.9, and with file explorer focused a multi-selection present, pressing Space opens the last-selected file (clearing the selection), and pressing F1 opens some sort of help dialog. If you’re referring to pressing Space+F1 in sequence, to me that seems to open the last-selected file and the help dialog.
Either way, none of these simply clear the current selection, so that different range of files can then be selected. For example, doing this 
requires using the mouse to reset the selection, or requires opening a note with Space and then focusing the file explorer again, AFAIK.
To me, Esc generally means escape from the current context into the parent context if there is one; i.e., Current context = multi-selection within file explorer? Escape to file explorer with no selection. Current = file explorer with no selection? Escape to the “main” content (e.g., a note, canvas, wherever the user was before they focused on file explorer). Current = settings view? Close settings view if there are no unsaved changes/warn about unsaved changes. etc. 
So, if the user is already focused within file explorer and a multi-selection is present, pressing Esc to clear the selection is the most intuitive way to do it, IMO.