Was there any particular reason for that or they simply hadn't decided on the new actor at that point.
McCoy is is the only one of the classic era Doctor I can really remember anything being said about the casting (recall that was some concern as his main claim to fame before Doctor Who was a stage act involving ferrets).
Can any one remember how the news came out of the casting of McGann? Iirc it did get some bigger coverage because it was going to be a tv movie etc etc.
I remember that there had been a lot of speculation for some time as to who would play the Doctor for either an American movie or TV movie. I'm pretty sure it was a reasonably big deal when Paul was announced. I can't honestly remember where I first saw or read (could've been a national newspaper, TV or a genre/film magazine) it but I do remember a big interview with him and article on it in the Independent newspaper within a day or two of the announcement.