The action states: If this Push is interrupted by Destructible Terrain, that terrain is removed and the Push continues. If this Push is interrupted by Impassable Terrain, this model suffers 2 damage.
If the only terrain that would ever Interrupt is the combination of Impassable Destructible it could have very easily been worded:
"If this Push is interrupted by Impassable Destructible Terrain, that terrain is removed, this model suffers 2 damage, and the Push continues."
But it is not. There is first a clause for interruption from Destructible Terrain, then a clause for interruption from Impassable.
If the model were to Steamroll a Pit Trap Marker would it not remove that terrain and continue the Push?
As for the point I tried to make on terrain removal timing
Interrupting stops a model at base contact. The interruption precedes the terrain removal, which precedes the Push continuing.
For example: The LE Steamrolls a Pit Trap Marker. It would Push to the terrain, interrupt here, remove the Destructible Terrain, then continue.
For the LE Steamrolls an Ice Pillar: It would Push to the terrain, interrupt here, remove the Destructible Terrain, suffer 2 damage, then continue.