Well I knew rpm limited coils were being used in chainsaws but they now appearing in the string/brushcutter line now too so it is possible to have the same problems of cut outs at full throttle if you exceed the max rpm set limit.
These manufactures are making the low end stuff so cheaply and of lower quality parts that they must limit the upper rpms to prevent damage. It is also most likely to meet government regs much like maximum blade tip speed we have on mowers. Limits like how far the string trimmer can throw a peddle or how fast a chainsaw can cut you leg off.
On the chainsaw cutting off your leg I wonder if that is a properly sharpen chain or a dull chain. I get chains in so dull that they are basically de-barkers.