Its not forced mate until 6...Kc5??, where 6...Ke7 is bad also because 7.d6+,but its not forced yet. Also 8.Qd2+ Ka4(forced) 9.b3++ is faster way to checkmate
It's not forced but if you try it against the computer, the computer will almost always play Ke7 and afterwards, always plays the line that I showed. That's why I called it a forced mate. Your accelerated mate was pretty clever though :).
The Whale (1. e4,e5 2.c4) doesn't seem like that bad of an opening. However, is is truly good? By the way, this opening kills the non-live Medium computer: