This has been discussed at lenth (and competent) in the comments on the article announcing the Two-Tim-spacewalk a couple of days ago.
So it seems to be about reducing suit stiffness due to high internal pressure.
This means you have to increase the oxygen content in breathable air to keep partial pressure of Oxygen constant.
Helium is used to replace Nitrogen in high-pressure environments because Nitrogen has toxic effects on the nervous system at high pressures. So this is not useful here. Using Helium also increases the problem of outgassing ("the bends") when pressure falls, so this is even less useful.
So this is all about a slow decompression to get to spacesuit-agreeable low-pressure while avoiding outgassing while keeping partial pressure of oxygen constant.
Maybe one should switch to Arthur C. Clarke rigid suits...