hi!
Yes, you are totally right!
We don't have the "if only one implementation of the interface is available" feature - but that is a great idea to have one.
Hence, you need to name your DoSmthReallyWellService bean as "IDoSmthService" so petite know the real name.
But this gives some nice ideas! For example, if bean is not found, we can use alternative set of names, from all the interfaces it implements. So when bean is registered by default name (not explicit one), we can simply register these 'add-on' names, and this is going to work.
I will add this feature very soon, for 3.7!