Aye. A plot can easily be expanded without breaking. But you have to tie off some branches around the times new ones grow in. If going by the examples above, Robert Jordan failed to do so and had trouble towards the end, whereas GRRM keeps killing major characters, effectively terminating excess branches.

We'd rather have a slightly vague, convoluted plot with lots of entropy to mess around with than a plot that is railroaded along a single, unbranching set of tracks. So long as the main story can be moved forwards even as branches do their stuff.