That is certainly one way of doing things, though in my opinion the people who get impressed are those who don’t understand what is involved so I probably don’t want to impress them.

When I do a repair my aim is usually to completely hide that anything has been done. So in this case a simple glue joint is likely sufficient, however if I wanted belt and braces I would add a floating tenon or 2 (still invisible), but of course after the joint has set you can easily drill a few holes for dowels, that they are redundant for the joint strength though of course doesn’t matter as you can use wood for the dowels that doesn’t completely match the stair tread for added emphasis ;) .

As to over engineering it is certainly better than having items fail, so I usually ere on the side of “too much is only just enough”