If so, that's a thankful addendum to this announcement.
Edit: yep, in settings, logins and passwords, there are two toggles, one to allow Firefox to fill in passwords for web pages, and one to allow Firefox to fill in passwords for other sites, which takes you to the Android password manager selection section.
Basically: when you focus an input textbox Android asks the service for autocompletion, and then you can choose one of the options which is entered as if the user has typed it. The service already has the password, and the destination app can only get it when you select it (same as if you write it yourself).
In the opposite scenario when you enter data in some inputs Android asks the service if it is interested in them (but without sending the content). If it does, it asks the user, and only when the user accepts the password/content is sent to the service.
In any case, you need to explicitly choose if you want to use or change a service for this purpose, and only one can be enabled at any time.