Please help explain this support gem problem

I don't understand the support gem situation for Righteous Fire.
I see now in PoB that Controlled Destruction will not work with RF. So I was trying to see which ones would, and I see that this fairly famous person Pohx here
https://www.poe-vault.com/guides/righteous-fire-inquisitor-passive-skill-tree-gem-links
has a very popular RF build (which I am not following), but just looking at it makes my head spin. I don't understand why he uses purity of ice and focuses on cold, but my main question is this:
Why does this build use Swift Affliction in the RF setup?
RF doesn't have a duration, nor does it hit?
When I put in Swift Affliction in my PoB, nothing happens (as if I had socketed nothing), which is to be expected. When I deactivate Swift Affliction in Pohx's linked PoB, the damage goes down. What am I not understanding?
Thanks in advance

The max res thing is probably melding of the flesh.

Swift affliction will work with RF if you support it with lifetap as that will give it a duration tag.

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gladiatorpie wrote:

The max res thing is probably melding of the flesh.

Swift affliction will work with RF if you support it with lifetap as that will give it a duration tag.

Thanks!
I'll have to look up what melding of the flesh even is ...😅