It's not a SIMM-size limit; it's a limit of the logic board's memory controller. The Color Classic, for example, comes with 4MB RAM soldered onto the logic board, and it has two SIMM slots, in which you can put 4MB SIMMs. That would make 12MB - but the CC can only see 10MB. AFAIK the same basic situation holds with the Classic II (even though it has only 2MB of soldered RAM.)