Changing "suggested" block size when burning a .cdi image - "unlikely event"

[frappuccino]

I am interested in the discjuggler block size paramater. The discjuggler site says this about block size:

"...In the unlikely event that DiscJuggler cannot detect the currently mounted CD Image contents, with this control you can suggest a block size. ...."

Therefore, does this option really need to be set when burning well formed .cdi images?