I really don't understand where this misperception about I-beam vs. H-beam came from.
H-beam rods have the potential to provide better strength and stiffness in the areas most highly stressed in a high power turbo application (high compression loads) with less mass. I-beam rods are typically preferred for a normally aspirated application where the tensile loads are the biggest concern.
That is not to say that there are not I-beam rods with sufficient strength for a big power turbo application but I am saying that this strength is achieved at a weight penalty in comparison to a well-designed H-beam rod.
This understanding comes after detailed discussions with Arrow which produces some of the best quality rods in the UK. The produce both I-beam and H-beam profiles and have done detailed FEA analysis of the distribution of stresses in the different rod designs. For the type of applications in question here, they would always recommend an H-beam type over I-beam.