Thank you @Nathan_Bossett really apprecaite you taking a look at the weekend.
Just to confirm Is Rhino 8 is reporting inside yes?
The points were generated by sampling along the domain of the line.
This geometry is from a larger file from one of our CNC customers.
They seem to have been really unlucky as they have surfaced two Rhino geometry bugs in the same file! (the other is Mystery - Why does Join give an Open Curve? - Rhino / Rhino for Windows - McNeel Forum)
Does look like Rhino 8 resolves both though 
good reasons to make the move to .net 7 and upgrade
Presumably the tuneup for these algorithms won’t reach Rhino 7?