It's not a standard, more a design trend.
I agree that the T-Slot system needs to become the standard for ASA mounts. It was as far as I was concerned at KEE and thanks to Jack Wood for providing the files so we could make them compatible where possible.
I remember someone made a T slot adapter to rail, maybe CP?, that might allow you to swap parts around to fit your needs.
There have also been options for the Mini/Axe that allowed a drop forward to be used, but I don't think they were very successful and fell to the side.