To me it means they are showing effort and interest in the workplace environment, and not just making it a drab cubicle farm, and messages something beyond just the actual stuff like dogs and music instruments.
BTW, nothing personal but I hate trying to explain my writing as I am a big fan of metaphor and ambiguity.
I have dogs in my office. They run around and bark all the time. Their presence shows to me that serious engineering work is not important, but the image of being a "startup" is. The idea of a musical instrument being played while I am trying to focus on engineering is horrifying.
There's also a whole world of potential designs besides "drab cubicle farm" and "kindergarten mashed-up with ComicCon". For example, the 37signals[1] office.
If they want to show effort and interest in the workplace environment, they should try providing private offices with doors that close.
BTW, nothing personal but I hate trying to explain my writing as I am a big fan of metaphor and ambiguity.