grunt-cbr-styles-bundles task—watches bundles only.
Let's say there are 35 pages on a project. Three of them use "special-offer" block from project's library, so if we change this block we don't want to compile all 35 pages which will take some time.
grunt-cbr-styles-bundles-watch will see that only three pages use the block and compile only them.
No options so far.
To prevent collisions with other more helpful tasks. You are not supposed to run it manually anyway.