SwOS is designed for very basic switching use cases - i'd be very surprised if MLAG and L3 made it in there. It might not be the best use of development resources considering it's going to take a lot of work to get those features tested and stable in RouterOS.
I understand what you're describing, but I think SwOS is particularly underrated. It seems to me the vast majority of tasks that are needed in hardware from a MikroTik switch can be done with SwOS (I only started using it about 2 months ago while I had been using RouterOS for many years prior).
I'm curious, what switching capabilities do you usually use or see used in RouterOS that are not available in SwOS (Excluding MLAG and L3, of course)?