You're more right than the parent comment --- algorithm agility is, I believe, an increasingly discredited idea among cryptography engineers --- but there's truth to the idea that a serious PQC scheme is going to be paired with a conventional key exchange, so that a new lattice crypto attack won't break the whole handshake. That's not "agility" --- the schemes will almost certainly be hermetically sealed, one PQC KEX and one curve KEX --- but it does mean you can deploy PQC now without compromising your whole cryptosystem.
The big issue here is that this observation doesn't break the premise of the article. It remains true that we don't know enough about how real-world quantum computers, if they ever exist at scales useful to attack cryptography, will work.
The big issue here is that this observation doesn't break the premise of the article. It remains true that we don't know enough about how real-world quantum computers, if they ever exist at scales useful to attack cryptography, will work.