Because it also targets the CoCo (Tandy's Color Computer sold through the defunct Radio Shack retail chain).

Yes, 6809 was an amazing microprocessor. It was doomed by the vaporware-ish Zilog Z8000 and the long delayed Motorola 68000 (the combined effect was to keep potential manufacturers of new 6809-based SBCs waiting on the sidelines for the new 16-bit generation microprocessors, while their much older 6502/8085/Z80/TMS9900 based boards skyrocketed in popularity...making it increasingly difficult to transition them to the far superior, but slightly software incompatible, 6809 microprocessors. Someone even had to eventually make a65C816 to keep the 6502 users on life support. The delayed 68000-series machines (which, like 6809, also broke software compatibility, but offered superior clock rates and 16-bit computing) came in too hot (the high-end workstations like Apple Lisa, SAGE, etc. followed by Mac, Amiga and Atari's knockoff of it.) This temporary market phenom also was probably the driving force behind Acorn/ARM, which is finally "taking over the game" (33 years later lol) after having been put on steroids by a few chip designers (first DEC with the StrongArm, now Apple with M1 Ultra, soon Ampere with the Siryn).