Sure is all tris under the hood. But for modeling and a clean topology you might want to have quads. Edgeloop tools simply stops at a tri. And sds'ing a tri can lead to a pole, which you might want to avoid. So it can make sense to model away a tri. Here two solutions to get rid of the tri at this place. But keep in mind…
you will always have triangles, that is normal. you have to terminate loops somewhere like that sometimes. if you get to animation and find it to be a problem (you most likely wont) then you can just terminate the loop somewhere else. don't waste time on this, it's a common beginner mistake to read "use quad topology" and…