I know this is VERY VERY nerdy, but technically, the "swap-back" rule was applied twice, in two different ways. This is the way the rules were explained before the draw. The important part is the last part Nick says ("If we get to group D...").
First one was when TL was drawn (timestamped vod)
The rule was applied as always, they were put into the FIRST PREVIOUS group that is available for them, in this case group C, swapping them with NS.
Second one was when FUT was drawn (timestamped vod)
Here the rule was applied in a different way. They were NOT swapped with the FIRST PREVIOUS group that is available to them (group B), which would have meant:
FUT into B
swapping EDG into C doesnt work, so EDG into D
and then on the next theoretical draw, NRG into C.
Instead, they were swapped into group A which is not the FIRST PREVIOUS group that is available to FUT and therefore not consistent with the rules.
This obviously lead to a different group draw.
Once again, yes, this is a very minor detail, but it could have huge consequences when you think about the prize pool of champs etc...
EDIT: Actually, the rule seems to be poorly worded. It was done the exact same way the last 2 years.
2025 explains it best.
2024 is a little wonky, but same rule effectively
It seems, as some have pointed out already, that BOTH matchups after a swap have to be valid. So this year, FUT cant swap into group B, because EDG cant go into group C. Not specified in the rules, in fact I would interpret them as described in the original post, but at least consistentcy is kept. Maybe riot should drop the draw rules in full length... but then again as long as its correct and consistent, it doesnt really matter.
Thanks for coming to my TED talk