If you noted, I mentioned that using this method requires a good amount of caution. I have been doing this for quite some time...just cutting tough weed growth and small saplings to clear a path around trees I am getting ready to chainsaw. Only A FOOL would try to cut rocks and fence wire...or make such an assumption.
For that purpose they bake solid blades for brushcutters
Some have Carbide tip & others have a length of chain saw chain as well as plain sharpened teeth.
These are safe to use.
A lump of saw blade breaking off at 9000 rpm will go right through you foot, boots & all.
Brushcutter blades are designed to bend & buckle not shatter like a saw blade will do.
And as for not finding rocks & wire, you should see what turns up in the middle of a 1000 acre paddock with no road for several miles.