Jock, welcome to Druid Glasgow!
You have cut right to the heart of the Mystery with your observation about the Necropolis.
The Necropolis was once known as Dun Chattan and was the site of a Druid sanctuary dedicated to the moon at the time St. Kentigern arrived in town, according to renegade archaeologist Ludovic McLellan Mann.
There's a related thread where you can download a scan of Mann's theories on Earliest Glasgow
here. It's fascinating stuff, but his theories are more than a wee bit controversial as he never revealed any of his sources.
Mann also excavated the Cochno Stone and Knapper's Farm, it's worth checking out the rest of that
Druid Glasgow thread for more information.
The Necropolis is also at the heart of the Glasgow Network of Aligned Sites described in Harry Bell's 1984 work 'Glasgow's Secret Geometry'. There are a couple of posts about it on that other thread.