Alternatively if you want to take it a step further, you can use a trigger to set the flying height of units depending on what region theyre in to make them match the height of the doodad.
(units would still 100% behave and be target-able like ground units and you'll have to surround the doodad with pathing blockers)
But this would allow you to have like multiple levels of height and save you a lot of time on manually placing down hundreds of invisible platforms.