[South]

They probably wore trainers in the past but they were stuck behind a desk so the viewer would never know

I do think this has been been blown totally out of proportion. 
Normally Sophie wears heels, there could be multiple reasons why she might not be able to which may not be associated with dress code, some could be medical. What would you suggest in those instances she can not present the news or do her job, that would be discriminatory.