Images listed prior to version 3.5 are not found on quay.io/projectquay

The Project Quay documentation mentions version tags of Quay and Clair which are not present on the quay.io/projectquay registry.
https://docs.projectquay.io/upgrade_quay.html#_upgrade_to_3_4_6_from_3_3_z
The oldest version of Quay available on the registry is version 3.5.1 (the documentation lists a 3.5.7 that isn't on the registry).
As for Clair it's even more off and most likely references versions as used on Red Hat's registry.

This is most likely due to a mix up in the split between he community project and the downstream Red Hat product.

And anything newer than 3.5 uses placeholder tags.