It was because escena admitted defeat on their northbridge design and in the meantime Eyetech learnt about the artica s, which lead to the A1.
Meanwhile escena where supposed to be developing a PCI bridge card that would attach to classic A1200 to allow Classic amiga hardware calls.
The original plans was for a port of exec to ppc and the rest of the os to be in 68K
The bridgecard would be needed to allow OS4 to run on the A1. The chipset dependencies would be removed and OS module to be ported to ppc by OS4.2
However, the bridge card never materialised so in ensence OS4.2 became OS4 aka a shed load more work but a pure PPC, hardware dependencies removed OS.
OS 4 has the frame work built in to map an AGA call, in escence the chipset could be emulated.
People have hinted at building such traps from the UAE source and is deamed quite feasable.