If a user accesses start.atlassian.com and gets redirected to team.atlassian.com which is an Atlas feature.

On team.atlassian.com page, there are Atlas features available which are accessible when a user/team opt for Atlas (full experience).

From users' perspective, 'start experience' (team.atlassian.com) is confusing because they can't access Status Updates, Projects, Goals, Teams and use them.

If Atlas is not enabled for user/site, then these features shouldn't be available at the start experience.

Related article community article.