Help with Geometry and the diagonal support of the goal

We have been teaching our students about 3-4-5 right triangles and how that works for VEX IQ. We use the triangle for structural bracing and teach our students to count holes and watch the structure align itself and stiffen up.

Conversely we teach our students that forcing a beam and a pin together is “bad practice”.

That means a 1x6, 1x11 and 1x16 connect to pins based on the 3-4-5 right triangle theory.

This year’s goal panel has a diagonal 1x18 beam as a brace. How did the design team get the rigid body CAD models to accept that?

Can someone explain the pre-stressing thinking for the goals.