I can't believe I had never heard of that before. Fascinating.

A question if you can answer it. Wikipedia says:

When close proximity during this critical period does not occur—for example, where a brother and sister are brought up separately, never meeting one another—they may find one another highly sexually attractive when they meet as adults

The addition of "highly" seems to suggest that separated brothers and sisters find themselves especially or unusually attracted to one another. Is that the case or is Wikipedia just adding unnecessary adjectives?