Attempting to call the WebAPI like:

Code:
http://api.steampowered.com/IDOTA2Match_570/GetMatchHistory/v1?key=__KEY__&hero_id=4&game_mode=__X__&matches_requested=10
where __X__ is an integral number which corresponds with the values at this url. The response matches appear to be identical - and not filtered by any particular mode - regardless of what value is given for the game_mode parameter.