Auto thrust would control your speed at the pitch attitude you selected and naturally if the pitch was too great the speed would reduce until flight control laws would kick in.
In my opinion a crazy and dangerous idea to have an aircraft that is not speed stabile.
This is not an Airbus vs. Boeing thing. This is Airbus against anything that has otherwise ever been build. This FBW itself it not a problem, it's the way that they implemented it.
With a conventional aircraft that is in trim, the nose would pitch down to keep the trimmed speed (unless active back pressure on the controls). That the speed just decays until protections (hopefully) kicks in seems like a recipe for disaster.
Like with AF447, the F/O held the stick back the aircraft actually trimmed itself to fly 60 knots or the stop of the stabilizer, because the protections didn't kick in. A back pressure which in itself would have felt highly unnatural in a conventional aircraft, since a significantly pressure would be required (here only the force of a tiny spring or whatever keeps the stick centered when no force is applied).
In a conventional aircraft no one would ever have held full up elevator, simply because it would have felt unnatural and uncomfortable requiring quite a bit of muscular power. Secondly the stabilizer would not have moved and third the aircraft might have recovered on it's own as soon as someone had let go of the controls.
Makes you wonder how it ever got certified!