Your use of ProtonMail+PGP is not how people expect ProtonMail to work when it is claimed to be encrypted email. ProtonMail+PGP is no different than GMail+PGP or AOL+PGP or FastMail+PGP or $coolNameMail+PGP. So what's your point?

Anything+PGP can be encrypted. You still have to use PGP which means creating public/private key pairs, store them correctly, and understand when to use the public key and when to use the private key. You still then need to know how to exchange keys in a trustworthy manner, but that's after you convince someone else to do all of that on their end as well.

So yeah, it's dead simple <facepalm>

What GP likely means is that a Protonmail user can exchange encrypted emails with a non-Protonmail user without doing anything except importing the non-Protonmail user's keys once.

This could allow a single technical user with an elaborate PGP key and email setup to convince his or her social circle (or at least email circle) to switch to Protonmail and follow a set of (comparatively) simple steps to get Proton to recognize the key to their non-Proton address.

Thereby having PGP-encrypted conversations with users who don't know how PGP works, but followed their friends' instructions to use a slightly different webmail interface. Meanwhile the technical user can use a smartcard, a self-hosted email server, or other madness that a normal user would never tolerate.