Not true, all companies need to comply with POPI irrespective of their size. Even a Informal Spaza shop will be required to comply if they process any personal information
You will run the risk of using documentation from other countries, or companies which are not compatible to your needs. Meaning you will not be compliant
If you process and record any personal information during the course of your commercial activities (even if your a sole proprietor), then you must comply.