Yeah, I was testing the arcade expression using the field calculator before I setup the Attribute Rule in the EGDB on the point feature class.
Eventually I got it to working although I had to create a new point feature class table with the projection set as WGS84 (WKID 4326).
var new_point = {
"x": $feature.longitude,
"y": $feature.latitude,
"z": 0,
"spatialReference": { "wkid": 4326}};
Geometry(new_point)
With decimal degrees populating into the Latitude and Longitude fields, upon the record's insert into the table, the geometry is calculated and the point displays in the correct location.
For some reason this does not work for projected points in a Transverse Mercator type feature class and I have not found out why that is.