1) If a software fix is not possible, Apple will end up replacing your device, even months after you bought it.
# they might not replace it, they might just repair it as i talk to one of their customer service online, they said after 14 days, there will not offer replacement, they will repair it.
2) If a software fix is possible, Apple will have no incentive to change the hardware and choosing to "wait 2 months" will not get you different hardware. If you insist on getting different hardware, the wait will be at least until the next refresh of all hardware, which will be 6-12 months away.
# software fix might be used to hide the problem or compromise on battery life or something else, if you trust apple then its ok, but not everyone trust apple. they might do somthing to cover the hardware fault. who knows. and you don't have to wait for 6-12 months, because if its a faulty chipset, they will be replace in the next batch of product, which may be just 30 days later.
3) The 13 inch comes with a different build of OS/X. Maybe support for the 13 inch simply wasn't finished at the time fo release. Who knows how many "fixes" and "work-arounds" OS/X contains for the 15 inch version and other Mac's. Just because OS/X manages to avoid issues on the other models doesn't mean they're not there.
# why you think the 13 inch come with a different build of OS X compared to other OS X machines??? do you have evidence? I actually erase my HDD and installed the lastest build of OS X, doesn't remove the error message in system log at all.