Technically it's not bestiality - animals cannot consent - this is more like being a furry since both are consenting adults.
Halsin is a Druid that can shapeshift and is fully sentient in his animal forms. So it ain't bestiality, otherwise you could say having sex with a centaur/werewolf/harpy etc... is also considered bestiality. If anything the scene was hilarious and a good presentation of how much freedom the player has in the game in terms of story.
I invite you both for a quick mental exercise: picture the 'bear' scene in your head, but image Halsin physically turns into a 6-year old child instead.
