Break-in prop
Cruzomatic,
The intention of that prop size for break-in, is to give the engine a relatively light load, but at the same time to have the highest possible flow of cooling air over the engine.
That is why a different, larger diameter prop with a similar load factor, would not suffice. A larger diameter prop with a similar load factor will need to have a much smaller pitch.
The smaller pitch will "pitch" too little cooling air at the engine, causing it to run hotter than its OEM intended, for a good break-in procedure.
Also, starting a new engine is easier with a larger diameter prop, especially for people who still use their fingers, or a "chicken stick". So it is tempting, but don't you dare do it.
Sincerely,