That's not the case, as there are no hidden buffers in vis. If a file is open, it is shown on the screen as either a horizontal or a vertical split. That's the only way to edit multiple files.
It would be really hard for me to switch to an editor without persistent undo.
A related comment on buffer management from the author of the project: https://github.com/martanne/vis/issues/300#issuecomment-2160...
I managed to live without hidden buffers so far, though I accept that they are convenient.