Not only does it show textbook RSA, it doesn't even show signing!
There are two secure ways to use RSA: as a signature scheme with appropriate padding (PSS), or as a Key Encapsulation Mode (KEM) which inherently doesn't require padding.
The general rule is that if an article on RSA includes anything about "encrypting a message" it's naive and outdated, and should be ignored. RSA encryption is slow and error-prone. RSA signatures are slow to generate (though fast to verify) and error-prone. RSA-KEM is at least not any more error-prone than the rest of cryptography, it's just slow.
There are two secure ways to use RSA: as a signature scheme with appropriate padding (PSS), or as a Key Encapsulation Mode (KEM) which inherently doesn't require padding.
The general rule is that if an article on RSA includes anything about "encrypting a message" it's naive and outdated, and should be ignored. RSA encryption is slow and error-prone. RSA signatures are slow to generate (though fast to verify) and error-prone. RSA-KEM is at least not any more error-prone than the rest of cryptography, it's just slow.