I'm a bit late, but this is referring to ditching RSA only for encrypting a symmetric key. The algorithm is vulnerable to side channel attacks since it expects

I'm a bit late, but this is referring to ditching RSA only for encrypting a symmetric key. The algorithm is vulnerable to side channel attacks since it expects the plaintext to follow a certain padding. The method only has 6% use today and is generally deprecated for DH. For DH, RSA is still used purely for signatures. RSA is not used to hide any data.