What if someone comes in with a gun pointed to your head?
It's why the guide is pinned there in the first place. Read through it again carefully. It emphasizes traders to meet up in public places where there are so many people to avoid scenarios where one can be robbed on gun point or mugged minus any witnesses.
Personally, I have heard some cases where people were robbed off their bitcoins under gun point because they chose to meet trading partners in secluded places.
Such operations should really only be done through specialized services. For example, like how Interactive Brokers works.

A trader creates their account in special software structured

as a fund. An investor can then invest money into that fund while maintaining full control, being able to withdraw funds at any time — of course, subject to market slippage if there isn’t enough liquidity in the order book.
Both the investor and the trader are protected, and there’s no need to worry about anyone stealing funds. Additionally, everyone can monitor the account in real-time.
Direct in-person meetings then become mostly formalities, since there’s no need to transfer funds directly. The fund manager sets management fees based on profits, and all transfers and calculations happen automatically. Everything is formally documented as an offer for the fund. It’s really quite simple.
