Your aerospace-technology link refers to the Flight Control Computers: these are used for the flight director and autopilot, not to provide a "fly-by-wire" input to the flight surfaces themselves.
Your second link to the luftfahrtmuseum seems less ambiguous, but I believe it to be in error, or at least misleading. Here is what
Airbus itself says:
"...In 1988, the A320 was the first commercial aircraft to enter service with an electronically managed flight control system (‘fly-by-wire’) and a side stick controller..."
The A300 initially entered service in 1974, and its'
primary flight control system is still conventional on all except a single, highly modified A300-600 called the "Beluga", which is a strange looking aircraft indeed.
This link may help to clear up some of the confusion:
"...In the Airbus A300FF, that entered the market in 1981, the aircraft's communication/navigation equipment communicated with the auto-flight system via digital data buses. The Boeing 757 and 767 followed in 1982, already offering digitally controlled CRTs which replaced several conventional electro-mechanical flight instruments.
By introducing the Airbus A310 and A300-600, the application of the glass-cockpit concept was continued. For the first time, these aircraft featured a digital control of the secondary flight controls (flaps, slats, spoiler)..."
So we see that the -600 model has digital connections to the
secondary flight controls, but all of these controls can move only in direct response to pilot input. In other words, the flaps move when the flap handle is moved, and at no other time. There is no computer deciding or interpreting commands for these secondary controls; all they did was get rid of the cables. Does that help?
As to the "smoke": As the aircraft yawed away from the relative wind, it is very likely that one or both engines experienced a "compressor stall" as the airflow through the engines was disrupted. These events can cause the engine to produce loud bangs, smoke, and even fireballs, especially at high thrust settings, and they absolutely would occur under these circumstances. The airplane yawed so rapidly that the engines literally "twisted" off of the wing due to gyroscopic precession--imagine what kind of gyroscope several tons of metal spinning at 20,000 RPM makes.
I believe the NTSB will address this in their final report.