I encountered this expression in various texts. For example in this book SelfBrand - The evolution: Turn yourself into an authentic brand!, I found the following:
"One selling proposition". Be specific about your branding proposal. Don't disperse yourself. After all, you've selected a specific target so you need to spread out a precise message. Otherwise, you'll confuse the ideas.
In this context, I think it is an analogous way of saying that one should not deal with too many topics. After all, to disperse means to spread over a wide area/to go in different directions by definition.
Could you tell me if that is correct? Thank you!