Did the Saturn V’s stage 2 (S-II) use helium for filling space in its tanks? Why or why not?

Summary

I revisited the classic xkcd Up Goer Five and remembered something odd that I’d never learned the reason for. Stages 1 and 3 have clearly marked helium tanks (with the memorable euphemism “funny-voice air”). But Stage 2 doesn’t have any helium tanks marked. So my question is multi-part.

1. Did the S-II stage use helium for filling up tank space during the burn?
2. If yes, where and how was the helium stored?
3. If not, why did the other stages need helium, and this one didn’t?

Attempts to find this information

The first video I found (Saturn V’s Hidden Plumbing) claimed there to be “six enormous spherical helium tanks that sat directly inside the liquid hydrogen tank” (4:18), but no such tanks appear on any diagram I could find. The first video is contradicted by a second, similar video on that channel (The Hidden Pressure System That Kept Saturn V Alive), which claims helium was used in the LOX tank, but not the LH2 tank, which it claims used hydrogen gas. (1:45) At this point I assume that whole channel has AI hallucinations mixed in with the good information, so I can’t trust any of it. To make matters worse, when I was Googling this question, Google’s AI summary cited that video to say there was helium used for filling space in the S-II.

Helium was not mentioned in a much more reputable video (The Saturn V Stage II) except for use in testing the stage for leaks.

I read through the S-II section of this 500-page “technological history” from NASA: Stages to Saturn. There were detailed descriptions of the difficulties in manufacturing and testing the S-II, including the famous Phillips Report, but helium was again not mentioned, except for testing, and purging air from some insulation during manufacture. I was surprised by that, given how many problems they described with making and testing these colossal tanks, surely they needed to protect them during the burn?

Next I searched for “helium” in that same document. Turns out:

• The S-IC used helium for filling space in the RP-1 tank, and gaseous oxygen for the LOX tank. (p. 122)
• The S-II also used gaseous oxygen for its LOX tank. I could not find any description of space-filling gas for its LH2 tank. (p. 144)
• The S-IVB used helium for its LOX tank. (p. 144) The LH2 tank there used a combination of helium and gaseous hydrogen (p. 178). The S-IVB used in the Saturn V actually used two sets of helium tanks: a cold set for filling space, and an ambient set for operating pneumatic valves (pp. 179, 182). I understand the S-IVB has special requirements, since the flight plan calls for it to stop and coast for several minutes before restarting.

Unfortunately, I still couldn’t find information on keeping the S-II LH2 tank pressurized. I can assume it also used gaseous hydrogen, but that’s not spelled out anywhere I could find. And why wouldn’t it also need helium like the S-IVB did for that tank? Is the need to restart the only reason?