I use different services for different things. I have 3 email accounts at FastMail and 6 at ProtonMail. Also, some of it is inertia: I've hosted the MX for sneak.berlin at FastMail for several years (and have prepaid some time into the future), and have only been using ProtonMail for about one year (and the HOWTO article is recent).
The fact that FastMail might be subject to the new Australian crypto key escrow law[1] is a little bit worrisome, and I may not continue to use them in the future depending on how that plays out.
For things where surveillance is less of an issue, I prefer being able to use a plain IMAP client, which ProtonMail does not support. Their current iOS client is pretty lame, for example (although their web client is better, and I understand that their next major release will improve things a lot across the board). I mention the IMAP issue in the article.
That in short, the A&A bill is about breaking end-to-end encryption, which Fastmail has never had anything to do with. It’s scary-sounding legislation, and I reckon it’s misguided at best, but it honestly doesn’t affect all that many businesses [note I’m saying businesses rather than people; many affected businesses will be among the largest ones, serving consumers], because end-to-end encryption of communications is uncommon, because it’s so frightfully inconvenient for all parties involved, because now the server is necessarily dumb and the client has to do a lot more work, and things like searching are typically just altogether broken because you’ll need the full index on the client to do a search.
(And specifically of the domain of email, I wouldn’t trust first-party encryption; if you care about governments accessing your data, first-party encryption such as ProtonMail offers is almost equivalent to no encryption if you can’t verify the code that is running, since that party may be compelled to backdoor the code to steal your password. This is one of the many reasons that Fastmail has never implemented PGP, ⅌ https://fastmail.blog/2016/12/10/why-we-dont-offer-pgp/.)
But why referring to Protonmail and using Fastmail for yourself?