Well I think alias services and password managers are essentially not that different. It’s all based on managing your identities.
You should always store all information you give to companies in your password manager. This so you can remember what you told them, what they know about you and so you can also be verified. Also, that will help to know what is exposed in case of a data breach. It keeps you in control. That’s definitely a recommendation to make regardless of the structure.
Then I see proton pass which is basically an aliasing service as well (sure it currently relies on simplelogin in background, but it has full management control).
My expectation is that this will become the standard for all password managers. They will basically become identity managers who store your passkeys, email addresses, passwords, perhaps dedicated phone numbers, etc. Even Apple with iCloud has this to some extent.
I am making the prediction that also Bitwarden will improve management capabilities over aliases and likewise the collaboration between Fastmail and 1password.
I am not saying it should be on one place on the website, but I think it should be considered. Likewise, I do believe that eventually you will just have one place to manage this all. If we keep it seperate we might end up having to change it because for example SimpleLogin gets fully integrated in Proton Pass, which I think is super likely to happen.