Please add Dota 1 as separate category, as presented here:
Currently streamers are forced to use Warcraft III as game even though they are playing strictly Dota.
Unfortunately Twitch does not ingest MODs as streaming categories, and from a categorisation point of view that is nonetheless correct for us on IGDB: Dota 1 is indeed a MOD of Warcraft 3.
What we'd recommend is to reach out to Twitch Support directly for the creation of a bespoke category, they are able to do override on certain categories.
Alternatively you may ask here directly for a new category to be created: https://twitch.uservoice.com/forums/310210-discover?category_id=367945
Hope this helps!