10 hour battery life was achievable 15 years ago on Pentium M provided you under-volted, under-clocked, and had a high capacity battery.
You're desperately moving the goal post to ridiculous places. It's like claiming that walking on the moon is supposed to be considered normal just because the technology has been ready for a long time.
That claim is irrelevant, isn't it? I mean, what good does a "technically it's possible" claim do if a) no, it's clearly not possible outside exceptionally rare circumstances b) the average consumer device is way behind any of those outlandish claims.
The fact alone that you're talking about using/adding a nonstandard and exceptional battery is more than enough to throw out that claim.