From inserters, you can expect identical load/unload throughput, putting aside corner cases.
The problem is that there is no equivalent loader in SA that can fully saturate the belt. If you want to share blueprints, you need to use a solution involving inserters. Things start to get complicated when you need a few thousand of these belts, and all of it is just pointless boilerplate to set up a test.
Outside of Creative Mode, changes would mostly impact Overhaul Mods with their own loaders that support SA. However, it will still be in line with the expectations from Vanilla: load and unload up to the belt's maximum capacity.
Expected result after change(currently mod):
