Apple sticks to the Original Max at the time usually.
At the time these MacBooks came out, I don't believe that 4GB SODIMMs were generally available, so the Max was 2x2GB for a total of 4GB. Apple doesn't seem to update their original specs. I can't think of a single case where they have.
I would say, it seems, that about half of all Macs, Apple has produced, support more than they could at their introduction, because the larger capacity DIMM/SODIMMs didn't exist (then, at the time of the introduction).
I think it's because 4GB works for sure, 8GB doesn't always work. So it's easier for Apple to support. I believe 8GB only started working after a specific SMC/bios update, and even still some memory modules don't work, like the Mushkin kit I described above.
At the time these MacBooks came out, I don't believe that 4GB SODIMMs were generally available, so the Max was 2x2GB for a total of 4GB. Apple doesn't seem to update their original specs. I can't think of a single case where they have.
I would say, it seems, that about half of all Macs, Apple has produced, support more than they could at their introduction, because the larger capacity DIMM/SODIMMs didn't exist (then, at the time of the introduction).