Identical 16x16 3 colours (2 bitplanes) bobs makes it possible to cheat with
- hw sprites and sorting
- dirty rectangle copyclearing and sorting
- no-shift (narrow) blit checks
- repeated bob data
- no-mask minterms
- copper-driven blits
All of which are the most optimal conditions you can get on the Amiga. "Those who can, cheat" to paraphrase an old saying.