Hey,
So today I have spoken with ESRI Australia Support team, and they have gotten to the bottom of the issue.
I had not noticed that my View U_PROPERTIES_ASSESSMENTS did not have a unique field being used for its primary key. There were several rows that were duplicated, once these rows were filtered out of the view, it works fine in both ArcMap and ArcPro.
So what appears to be the difference between ArcMap and Pro is that if this view is added to Desktop, this software finds the first instance of each unique primary key, and keeps this row, after this it ignores any duplicate primary, and the user is none-the-wiser about the duplicated being ignored.
But what is happening with ArcPro is that pro will draw all the shapes on the map, all 20,000+, but it refuses to load the table due to a column being used as a primary key which contains duplicate values. This is not handled very well in comparison to ArcMap so I think it should be marked as a bug in this instance.
That being said, I also think ArcMap are not being warned that the view being used does not contain the full list of features.
The bottoms line (TLDR), I needed to make my primary key column unique for ArcPro to accept my data.
Cheers for all your comments.