As designed Latest Member:

[click here]

When the "Latest Member:" that is displayed on the main forum Statistics block gets deleted, that username is still displayed there, it should be deleted there I would think?

 

[wang]

That wouldbe updated when the Rebuild Board Totals Counter cron will be run. You can also run it manually to update the stats counters.

 

[Mike]

The value is cached as noted. The cache is only valid for 10 minutes so it will go away when this happens.

There are many potential reasons this could happen, so essentially it's considered an acceptable trade off (with constantly having to rebuild it).