The discrepancy of the favored indicator before and after the match is listed as a known bug in the blizzard forums by a message from Blizzard Employee Huginncord (Quality Assurance) in the thread "Known Issues 1.4.3 [Updated: 4/11/2012]"

> • **Favored messaging in the load screen sometimes doesn't match the
> favored messaging in the score screen.** 
> 
> We're investigating reports
> regarding inconsistent messaging in regards to the Favored status of
> player teams on the load screen when compared to Favored status on the
> Score Screen. Thank you for your patience while we look into potential
> causes for this inconsistency.

source:
http://us.battle.net/sc2/en/forum/topic/2267599524