Ah, that must be the research paper that is being referred to by this short video by the paper author: https://youtu.be/azDaPm13CT8?si=Z11qpbjNIwuhxdnB

In US engineering practice, "I-beam" shapes are usually W's not I's. W is for wide-flange. The W's are more efficient than the I's because the flanges are wider...to the point that I's are a specialty shape with specialty shape costs...at least in terms of availability/lead-time when structural steel is sold by the ton and probably a mark-up due to non-commodity status.

Rather than looking at different letters, perhaps look at different font families. Clearly sans-serif I-beams are structurally much worse than avec-serif I-beams.