This is really horribly wrong.
It isn’t. No “professional” trader would dream of following this advice. No profitable trader would dream of following this advice, either. No trader with any experience would, either. It’s exactly the opposite to what people should be doing.
The important thing is to allow the stop-loss to be determined by the chart, your trading-plan, your edge, and what you’ve tested and proven to be successful over the long term. Then AFTER determining the stop-loss, you work out from that and your pre-set risk-parameter what size the position should be.
Determining the stop-loss level from the percentage of the account is exactly the opposite of what anyone should do.
It’s really disheartening, to see “advice” like this being offered, here. It’s not helping the forum or its members.