The interactive foliage hight position problem almost nobody cares about?

I am using this method to get some grass interaction. It is working pretty good most of the time. It supports multiple characters and you can create different forces by having different Particle Systems. But there is one problem: The Z position of the grass affecting object doesn’t get considered at all. I semi solved it by only activating the particle system when the affecter object overlaps with a foliage instance. That works as long as there is no foliage stacked on top of each other. If there is stacked foliage, all foliage gets affected and I don’t know how to fix that. I googled it (even went to page 2) and the only dude who seemingly solved it is this guy. Does anybody know how to solve this?

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