A partly speculative answer, working backwards from the source code of Marat Fayzulin's ColEm, it appears to be a fixed-size sector dump. On line 52 of EMULib/FDIDisk.c you can see confirmation of the geometry you already know about:
8 sectors per track;
Line 406 lists FMT_ADMDSK (i.e. Adam disk) amongst those ...
I don't know the MicroBee, but grew up with CP/M 2.2 and 3.0 and its variety of floppy disk formats.
There were two different ways of implementing skew in use:
assigning the low-level sector IDs in a non-contiguous order, and simply access sectors by a 1:1 mapping from their logical number, resulting in sector ID sequences like 0 3 6 9 2 5 8 1 4 7,