4 to 5 seconds startle is probably not something you can roll back in Airbus. Up to three perhaps, personal experience from both sides.
Side note, after LOC* the approach phase self-activates.
I was blessed with good instructors on the 737 who trained me properly that an illuminated MCP button means it can be de-actiavated. Whereas what mode actually is active
needs to be checked by constant review of the FMA.
Never had an issue not noticing the managed speed jumping up, because the speed tape was the focus. Mixing up speed / heading / altitude selectors - different story, that takes longer than 3 seconds at times.
For A/THR disconnect, the instinctive way is the easiest. Put the thrust where you need it to, and then click-off. I do understand the setup of the incident flight was far more complex than that.
In my overall opinion, full escape from the automation trap needs more hands-on training than is being done. I am a great fan of slowly decreasing the level of automation instead of an instinctive and mostly premature all-disconnect. Yet when it needs to be done it needs to be done properly. All off, set pitch and power FDs off! Quickly and decisively.
Very often some sort of feature is left engaged by error of either ommision or bright idea. Which backfires by making the situatuon hard to read, process and prioritise.
My last flop was as simple as keeping the FDs on when doing a 90 deg hard avoidance turn having just disconnected the AP for urgency. Just to wait for the PM to select a proper heading target while I banked towards the safe side... error of a bright idea. 😟 The pitch bar with ALT* and A/THR in CLB did the killing.