There are definitely other reasons. Remember "Thoughts on Flash" [1]?
“First, there’s Open… Rather than use Flash, Apple has adopted HTML5…” — and CSS3, SVG, and HTML5 have indeed provided most of the capabilities that once were Flash’s domain.
“Third, there’s reliability, security and performance.” — which is really three things, each of which Flash has an outstandingly poor track record with.
“Fourth, there’s battery life.”
“Fifth, there’s Touch. ¶ Flash was designed for PCs using mice, not for touch screens using fingers. For example, many Flash websites rely on ‘rollovers’…”
Where'd you pull that idea out of? Google's not implementing the Flash player, only providing new API for the Flash engineers to build against, the same as they always have.
From previous statements and actions of Google regarding Flash (fixing security holes in a way that implies they have source code access), it is very likely that it is indeed Google that are doing this.
The real question is if this is true, why are they dropping flash for android?