You got me a lil bit. The speaker is in mono, yes, but that's not the problem. It's in mono as if the other speaker sound doesn't exist.
I might have made it worse for you, so I'll try and explain it in a somewhat easier way.
Consider a song with say singing and guitar.
With your earphones, lets say the singing comes out of the right earpiece and the guitar part comes out the left.
The problem with the SGR speaker is that ONLY ONE of these things is coming out. Lets say the speaker represents the left earpiece. Then you can only hear the guitar and you cannot hear vocals.
Please tell me you understood now