Hydrogen Causes Metal to Break

In layman's terms the way this works is that various chemical reactions can liberate atomic hydrogen (H₁), which occupies a very small space. If two H₁ atoms are around, they have a high affinity for each other, and will bond into an H₂ molecule. The geometric spacing of this molecule is much larger than the two H₁ contributing atoms. This produces tiny "cells" of high pressure that can distort small regions of the containing structure (such as pipes or vessels). This is the condition known as "hydrogen embrittlement" that pertains here.

Hydrogen embrittlement is normally only a problem at high temperature or high pressure

I remember a hydrogen fuel company who sold a conversion kit for autos. It apparently worked well until the blocks starting cracking after 10 000 miles or so.

The article talks about hydrogen embrittlement as if it is something new and a real worry.

A fantastic amount of work has been done in the past years on this topic. It will take a new approach for certain equipment but no big deal.

Like was pointed out - it is a problem of high pressure/temperature.