I recall at some point when Bill Cullen was a fill in host after Garry's retirement, the panel was introduced first, then Bill. I guess they thought it was awkward that Bill was already there, seated, and couldn't really make an entrance in the same way he did when he was a panelist. I think the producers just made this change for the second run because Garry Moore isn't Bud Collyer. Bud played it straight, and Garry liked doing bits at the start, so it's just a way for Garry to make the show his own.