There are a number of abilities that treat something as something else, specifically some kind of terrain in this case. For example, Grave Goo's Trail of Slime ability reads, "Enemy models treat terrain in base contact with this model as Hazardous...".
Crypsis Corps' Beneath the Leaves ability takes this up a notch, reading, "While this model is within 3 of Severe, Hazardous, and/or Concealing Terrain, enemy models treat the area within 3 as having those same traits."
Let's postulate a Seeker vs. Apex match where a Crypsis Corps model is within 3" of a Grave Goo model. Trail of Slime means that the Crypsis Corps considers the terrain in base contact with the Grave Goo to be Hazardous ("terrain in base contact" is an aggravatingly non-specific term, but that's another matter). Does that, in turn, mean that the Grave Goo and its teammates consider the terrain within 3 of the Crypsis Corp to be Hazardous, because of Beneath the Leaves?
I feel like RAW would say yes, but that seems like a weird, counter-intuitive, and hard-to-parse ruling. Thoughts?