I'm afraid you're both wrong, containers are an add-on, profiles are a core functionality.
That person does not want something new, they just want to use their existing workflow, which is possible, but inconvenient due to bad UX and ugly UI. These are their words, not mine.
As a user of both containers and profiles in Firefox I have to agree with them. The UX needs to improve and the UI needs to be prettyfied.
This has nothing to do with trust, a profile gives you a different set of add-ons, bookmarks, search history, saved passwords, cache and cookies, a container only gives you a different set of cookies.
This does not change the fact that container is a core functionality in Firefox.. and for some using addon is a matter of trust.. Also does not change the fact that chrome does not have anything like it..
Additionally Firefix also have profiles as a core funtionality, it already had it before chrome even existed so it had it much longer then chrome had.. But again is mostly hidden away..
You can access it with the command below:
firefox -ProfileManager
But as with containers there are add-ons to make as easy as chrome to switch between profiles.. Although i don't think there is an official one by Mozilla..