"Given that mobile phones probably the most complex pieces of consumer electronics in the world, it is IMO at least conceivable that there could be some "architectural" reasons for not having N-Gage run on E Series.."
I know what you mean, but I just don't buy it. There's too much evidence against it.
Smartphones are complex, but they're all the same software platform on similar computing hardware, so if they're working correctly they should be able to run the same software. For example the Eseries game Global Race ran fine on the N95 and N93, even though it was only developed for E90. And the fact that such a complex graphics-intensive title did run fine on Nseries and Eseries proves that there's no reason for Nokia-published games to exclude Eseries.
If there were really architectural problems, we should be seeing 3rd party software developers creating special versions for Eseries phones, but they don't, they just create one S60 3rd Edition version.
Windows PCs are even more complex, but Windows software runs fine on all PCs as long as it's they're the same Windows version with similar hardware specifications.
"would be interesting if someone in AAS could try to get to the bottom of that."
I suspect it's just Nokia trying to make a marketing decision look like a technical decision, in which case they'll never admit this to us.
It's like Sony recently bringing rumble to PS3 controllers because "they had overcome the technical difficulties". In truth, it was purely because Sony had settled a lawsuit with the makers of the rumble technology they wanted to use.
"I recall Tommi Vilkamo once explaining something about why the 3D Bar Code reader needed to be tested thoroughly and _separetely_ on each N-Series device. So perhaps there is much more to it than one thinks?"
The bar code reader was a program that depended on a phone's camera hardware, which is not defined by S60 standards. Different S60 phones often have completely different camera hardware, which would explain why each device had to be tested separately.