MC: 1.16.4
AS: 1.13.4
Observlib: 1.4.4
Curios: 4.0.3.0
This may be as intended as it functions fine with the use of ritual anchors assuming the stone structure edge doesn't impede over the Ritual altar.
A possible solution would be to have an open "shaft" in the center of the structure to allow the ritual area sky access if at an altar and not an anchor. This seems to already exist for the Ritual Anchor but it's not big/wide enough for the Ritual Altar since lens reflections may be used and it may also place stone above the crystal bringing starlight.