Selection and action are very closely linked in Dorico, which means that we can’t easily decouple them in undo/redo. But perhaps in the future we could have an option for undo/redo to skip to the next action, effectively folding all of the intervening selection changes into a single undo step. It’s not a high priority for us at the moment, however.
I agree that having more descriptive undo/redo messages would also be helpful, and this is definitely on our backlog.