Very enjoyable it is too! Thanks.
Quick question - Why "(later)"? Because it cuts through C&Rs perhaps? Many C&R designs have over-lapping designs. "(later)" could mean one day, one year, 2000 years ...
THis is what I've been on about. Because these basins, bullauns, whatever-you-call-em have been in use in recent times (see the folklore link on knocking stones) they assume they are more recent.
One at Glendalough (the Deer Stone) has milk folklore too, which is at least 1500 years old, probably much older. As I said the cultures of the time were very similar, if no the same.