[The Australian Panther]

I can't give you a definite answer. In practice, when there was a comic produced of a licensed TV property, there were often specific rules in place as to whether you used a likeness of a character or not.
At the time, Richard Chamberlain was a huge star from this show, so the artist would probably have been under orders to depict him accurately - and that is a lot of work. The artist may have just decided not to put so much effort into depicting Gillespie.

Link to the book: Dr. Kildare 2