Entirely a guess. I don't talk about anything that might be included in any NDA that I digitally sign.
It could also be a feature that Apple does not turn on for the older MB/MBP. Just like Apple did with the multi-touch trackpad, older model MBP were capable of multi-touch; it had to be enabled via a hack.
Time will tell, I just think it would be a "feature" to get a few extra people to upgrade.