If you are referring to the map you download from the menu "Download maps", and that are graphically rendered locally (that is what is downloaded are the data and the graphics is locally created) you are correct.
If you enable the Online maps plugin than you can tell OsmAnd to use some already calculated image tiles. These are downloaded from an external sever and cached locally (in the directory I said in my previous message). As far as I know these cached tiles are not shown under Download maps and I do not know any way to delete the cache from the app.
I assumed that the Original Poster was referring to these tiles/raster map
Just for information, to use these tiles (including the OsmAnd online tiles) you should first enable the Online maps plugin, the go to
Configure map
select the profile you want to modify
Select Map Source...
Select one the option listed (note that some of them are more suitable to be used as Overlay or Underlay map, if you select one of these the result would not be great). You can select more maps/tiles than the one listed in the first list you get, by pressing "Install more..."
I think that it should also be possible to save locally the tiles from some external sources or create them with tools like
OsmAnd MapCreator and use them offline, but I do not know the details.
AnyFile