Unfortunately, no. With Portal, you can do this using a Hosted Map Image layer, but to get this to work in AGOL would require an additional layer showing buffer polygons, which would need to be updated separately from the points layer. Still doable, but not as simple as you might want.
Arcade does have access to the $view_scale global in the symbology expression builder, but you'll find that even after a lot of fiddling, it still won't give you reliable results if you want real-world units.
- Josh Carlson
Kendall County GIS