OCS and ECS are 16bit and so is the DMA bus architecture for chipset<->CPU<->RAM. As you are programming the 16bit OCS/ECS and all chip/fast memory access is 16bit so your games are running on a 16bit computer ergo they're 16bit games.
Calling Amiga 500/600/1000/1500/2000 32bit systems is as wrong as calling the Atari Jaguar a 64bit console.
