the Multi-Account Containers extension always only added additional UI functions to manage containers. it was never a different container implementation. so they are migrating UI features from the extensions back into the core.
"Not all of the features of the add-on are available in the first-party version of containers just yet, we’re still building them out."
the migration is not complete yet. i expect that eventually the extension will be made redundant.
Except this announcement only lists features already available natively (also enable privacy.userContext.ui.enabled for them), that's why it's confusing.
"Not all of the features of the add-on are available in the first-party version of containers just yet, we’re still building them out."
the migration is not complete yet. i expect that eventually the extension will be made redundant.