G400S available Flash

I am looking at a project that may use the G400S but I have a question about the available flash shown on the product page.

The G400S and G400D show only 1.4MB available from the 4MB total. The G120 on the other hand shows 2.87MB from 4.5MB total.

Is there a reason the G400 is way less?

Sounds like the base libraries for the G400 are bigger than those required for the G120. Guess a larger CPU with more instructions needs backing by a larger lib