Type stability is important for performance, but I usually fine tune this aspect of my code after the interface and most of the structure has stabilized and I am in the optimization phase. So I would not necessarily want warnings about it by enabled globally.
Also, some forms of “type instability” are innocuous and handled well by the compiler.
I think the best strategy is to obtain this information for parts that need to be fast, but then do it in a detailed way, eg like