What would mAH tell you? Do you know the power consumption of the A11 chip, OLED screen, wireless stack, motion coprocessor, etc?
It's not like you can compare battery life between an iPhone and a JoJoMe $20 android phone based on mAH - that would be even less useful than an estimate of battery life.
On the other hand, a capacity in mAH is not the only spec about battery life they should provide. Each new phone tends to consume more battery, due to new processors, bigger screens, or other factors, so an indication of typical battery life is useful.
They may not be the only offenders but it bugs me that the tech specs don't tell you the battery capacity in mAH. Instead they give a relative number of hours and compare to previous phones. Those aren't tech specs, they're claims-- which they can say in fine print are unreliable.