> That's actually one of its advantages.
That was the marketing talking. When WP7 could only handle single core they said: why would you need dual-core ? Of course WP7 was strictly single-tasking and 'tombstoned' apps in order to start another. The only 'background' tasks were like MS-DOS TSRs.
When WP8 required dual-core they said: 'why would anyone need quad-core'. That was because WP8 did not support quad-core (now apparently it will do with 8.1).
> the lower-specced hardware it can get away with places less demand on the battery
Actually the _reason_ for multiple cores is to cater for idling with less battery demand. ARM chips can turn off the cores when not required and each core (or the last one) can idle at reduced consumption. So instead of using, say, 30% power at idle with a single core, a quad core can run at 30% of one quarter of the full power, or less if it has asymmetric cores.
Newer SoCs can also have lower battery demand than one from 2012 because of having newer manufacturing technology. They often have more functionality in the chip and this can also reduce power demands and, with fewer components in the phone, can save manufacturing cost.
Being stuck on 2 year old designs meant that Nokia had to sell at a loss (even when MS bunged them a billion a year) and hope that volume would increase so that eventually there would be at least break-even. Maybe that will happen. Meanwhile Mozilla has said that the latest chip could make a $25 phone because, basically, it will be a single chip plus a screen.
Being _old_ and lower spec does not make it cheaper.
> There's no intrinsic reason why that should be the case. New chip comes out that MS want to support, they can just as easily allocate engineers as Google can.
Yes there is. Microsoft must do the software for WP. With Android _anyone_ can tune the system to a new SoC. For example: Intel are tuning Android to their newer chips while tuning the chips for Android.
Android, and other Linux based systems, could also run on MIPS based Dragon chips or Intel or indeed any newer architecture.