BS an SSD is the same as Flashmemory. The Flash in the MBA is connected by the same interface as an SSD it is simply left wihtout to enclosure to save space that makes it no different.
The Instant on has little to do with Flash or SSD though. In normal S3 aka Sleep all data is in RAM and how quickly all the other chips (CPU, Northbridge, GPU, stable power, ...) wake up is up to the OS and has very little to do with an the SSD.
If Apple wants to change the wakeup time on the MBP they have to give us an OSX update or driver update or maybe it even needs a slightly different bios.
An SSD makes a difference if the computer is in S4 aka hibernation but you'll need a much faster SSD for instant on from S4 with 4 gigs RAM. It is pretty much impossible.
Aside from all that it is all just marketing. MBA still needs about 1 1/2 seconds to wake up and a MBP usually needs around 2 1/2 seconds. This 1 second really is not that big of a deal. If it needs a BIOS update all Macs will receive these short wakeup delays.
A Notebook is just more complex but in theory every notebook could be on as quickly as an iphone from sleep mode(S3). A Notebook also takes more energy and it needs more time to get a stable power supply at a certain level than the 1Watt a iphone needs.