I assumed we could use the 'Last Contacted tag for this.
Intercom defines Last contacted at as "The time they were last contacted by you, with an auto/manual message, or with a reply in a conversation"
But I see that this does not include if they received an automated tour. Even if the user has received a tour 2 days ago, setting the rule 'Last Contacted > 3 days ago' fails to exclude them.