No it didn't and you can even look at the source tree to spot it.
Want more proof? Google designed Android 3.0 Honeycomb exclusively for tablets and never released it on phones.
I'd love to know how that FACT works within your argument?
Do not confuse platform with UI.
The android platform was in fact designed to be cross platform. It's hardware inedependant and where there's conflict, Android being an open source platform can be modified to work.
Android is essentially a linux variant (but highly modified).
And like linux variants, you are not tied in to a specific GUI. Linux running KDE, GNOME, Unity, XFCE or even GUIless are all still Linux, despite have drastically different user interfaces.
Android follows this same key.
Android 2.x was designed for the small screens of the phones at the time.
They felt after testing that Android 2.x was a cludgy and terrible interface for the larger screen real estate of a tablet. So they Redesigned and built a new UI exclusively for use with the larger screens.
Learning from mistakes in both UI's, and learning that it's better to have a unified approach, ICS was designed with elements for both.
They are all, however, Deep inside, Still android, despite the different UI.