Please show me in my post where I stated I "don't feel that 4GB of memory is adequate" or anything remotely resembling that. It isn't what I wrote and has nothing to do with the point of my post.
You wrote about how 2.5GB average RAM usage was some mythical, perfect number, so nothing more could even be needed or used. My point was simply this: The OS will efficiently allocate the amount of RAM available to it. IF the OS has more RAM available it can keep more apps in usage while still having a reserve available.
Look at it as a ratio - on your 4GB phone the OS allocates 5/8ths (2.5GB) of the RAM for constant usage and reserves 3/8ths for buffering/fluctuations etc. At the same ratio, more RAM would allow more apps to remain open/available AND have more reserve available for buffering/fluctuations etc. 2.5GB is not some magic, perfect number of RAM usage.