Do either of you have a cite for this? I’m certainly not expert on this topic but I’ve done a fair amount of reading and thought there was a scholarly consensus for strong parallels among Indo-European religions.
Of course the details vary. In the ancient Irish royal anointment, the King fornicates with a sacrificial white mare. In the ancient Hindu ritual it is the Queen who fornicates with a white stallion.
The royal Celtic name Epomeduos (< ek’wo-medhu = “horse + mead”) reflects the ceremony, mead being the fermented honey imbibed during the ritual. Was it coincidental parallel development that the Vedic ritual is called Ashvamedha (अश्वमेध), cognate with the Irish name (although AFAIK no fermented honey is involved in the Vedic ritual)?
There are other specific parallels between the functions and rituals of Druids and ancient Brahmins, down to the ceremonial clothing color (white — also in each society the warrior caste wore red).