It isn't wrong. The challenge wasn't, "fly a route where the interior angles of the triangle equals 270 degrees." It was:

-Start at point A and travel a set distance in a straight line
-Make a 90 degree turn and travel the same distance
-Make another 90 degree turn and travel the same distance back to the starting point.

The flight path Wolfie demonstrated accomplishes that. It had two 90 degree turns and it ended up at the start point. Those were the only requirement. What a lot of other people are talking about is an equilateral triangle, however, that was not required to meet the requirements. What's probably not clear to you and others is that the sum of the interior angles is not an exact figure, it is a range with an upper and lower bound. One triangle may be 230 degrees, whereas an equilateral triangle will have 270. A triangle that meets the requirements of the challenge doesn't need to have 270 degrees.