Literally! The mathematical requirement for grid beam is that the width of the beam matches the hole-to-hole distance in the beams. Lego technic beams are 8mm wide, and the hole-to-hole distance is 8mm. Lego is small-scale grid beam.

Example grid beam tri-joint made with Lego Technic pieces: https://twitter.com/hugs/status/1619804592199577601