The list will remain empty, while there are many free 3D items there.
It looks like it’s more a referencing issue than a real bug, but still, i can’t list all the free 3D model available.
The filter “Pack type” was implemented only with packs in mind whereas the filters above can only filter assets (because packs don’t have the metadata yet) so there is no intersection between the 2.
As a workaround, paid assets that you don’t already own are not listed, only the packs are. So, you don’t need to check “Free” to see the free assets unless you own some paid packs.