Difference with Guest Stars in Opening & Closing Credits

[Swellin]

Did you find it strange different guest stars received different billings in with the opening or closing credits:

Here's an example

Opening in early seasons

Susan Howard as Donna Culver (full character name)
Susan Flannery as Leslie Stewart (full character name)
Leigh McCloskey as Mitch (only first character name)
Tina Louise as Julie (only first character name)
Mary Crosby (no character name)
Randolph Powell (no character name)
Jared Martin (no character name)


Closing in early seasons

Guest Starring:
Joel Fabiani (no character name)
Morgan Woodward (no character name)
Special Guest Star: Monte Markham (no character name)
Co-starring: Cartel members, secretaries and staff (no character name) except Fern Fitzgerald as Marilee Stone

With: Minor characters with just their actor names