Correct. Its designed that way.
You can only use sphere, sphiel, and cloth capsules per the nvcloth specs.
also cloth as a whole does not react to outside physics.
To get that to work you have to skin the cloth and create a PHAT asset to allow for the physics interaction - and paint the cloth with a value of around 5cm to make it look like its actually reacting.
In reality the phat asset is driving the physics. The cloth is just there to make it look more natural than it otherwise would.
Note that within the phat asset you can use whatever collision you want, since it’s unrelated to cloth.