The piece is at least as much about how emulator design (can) differ between emulators for arcade machines and emulators for 8-bit home computers.
Home computer emulators need to be able to handle all the software you can throw at it, while an arcade emulator need to be able to handle on the single game ROM which ran on it. It doesn't need to handle subtle behavior of the hardware which never manifests in the game output.
(Of course, the situation is different for arcade machines which could take different ROMs.)
Not to mention that home computers had a different set of devices to handle as well - eg. cassette drives, floppy disks and later small hard disks - often with their own controllers which had to be interfaced with the system somehow (using isolated I/O on CPU's like the Z80, and memory-mapped I/O on others like the 68000).
Home computer emulators need to be able to handle all the software you can throw at it, while an arcade emulator need to be able to handle on the single game ROM which ran on it. It doesn't need to handle subtle behavior of the hardware which never manifests in the game output.
(Of course, the situation is different for arcade machines which could take different ROMs.)