There's no marker, Buffo, just a model that gets placed. Since models can't be placed in impassable terrain, the deepstriking model can't be placed in impassable terrain, either.
Basically, your argument boils down to the assertion that all rules exist in a complete vacuum and never interact with other rules at all. This is so obviously wrong and absurd that I won't even bother to point out the near-countless examples of rules-combinations upon which the game relies.