Scandoublers that don't support 24 bits produce incorrect colors in ALL AGA modes.
Even if you have a 16 color workbench on your A1200, the 24-bit precision is constantly being used to show the correct 16 colors all the time.
Up unitl the Indivision: There was the commodore FF and others. The flicker fixer from Commodore but limited you to a palatte of 4096 colors, no 24bit
Then 16 Bit support was common after commodores demise with 3rd parts solutions.
The Invidision uses a 24 bit color chip to support a 24 bit pallete. There's no way for this thing to behave as a graphics card, where you get extra colors in a 256 screnmode and nigher resolutions. It just promotes every native AGA screen to VGA scanrates and removes the annoying flicker.
I uses it with NTSC modes as they run quicker. The AMiga is only generating 15lkhz signal. The Inidivusion promotes this to 31klhz. Using a DBLNTSC wit the Indivision is slow.
A really great product!