Heard the same theory on Peak Prosperity videos. That a engineered virus is unstable and will revert to its natural state in a few generations. We can certainly hope that is the case. It does not appear currently to be less deadly in South America, it is ravaging Brazil, Peru and Mexico. There certainly seems to be more then one type spreading in the world causing radically different death rates.
If it’s ravaging South America now then likely their strain must have forked from an earlier generation.