I agree that this is the wording of the comment - if having a PGP-encrypted message intercepted in transit compromises it, something has gone horribly wrong.
Fortunately, it's not true; the situation is actually much better than the comment suggests. As the Protonmail rundown points out, the better PGP clients should be unaffected, and secure even with in-transit interception.
Fortunately, it's not true; the situation is actually much better than the comment suggests. As the Protonmail rundown points out, the better PGP clients should be unaffected, and secure even with in-transit interception.