I know this changed because I notice this Invited By section is not there (in some cases). I can still see this on certain user profiles , but I believe this will not work anymore in the case that the user you invited was already on the forum. In other cases, user invites will be shown on the profile e.g. when they register for the first time from said invite link, so if you accepted an invite while you were already on the forum, then this “invited by” will not appear, but registering from the invite link permanently ties you to who you were invited by.
I moved this to a Feature topic because I believe the behavior you are describing is “by design”. It makes sense to only show who invited the member on their profile for that first invite that directly caused them to sign up.
That said, I do think it would be helpful for moderators and admins to be able to see a list of all invites a member has accepted somewhere obvious. The user admin would make sense. Perhaps it could simply be logged to the staff action log?
I made a tweak to that part of the doc to reflect the current behavior: