I think the reference was maybe about the butter vs. margarine controversy? That margarine was lauded as more healthy, but turned out to be actually less healthy than butter, due to hydrogenation producing trans fats which elevated cardiovascular risk.

Since mid-1990s, margarine no longer contains appreciable amounts of trans fats.

Butter also contains trans fats but these are ruminant TFAs which I understand are not so bad.

This is why despite butter composition being worse "on paper" there is no empirical observation that it is less healthy than plant margarine.