it should be obvious that a gain in altitude implies a reduction in speed if nothing else has changed,
In still air, yes, but in an area of convective weather, that's not the case....remember it wasn't exactly clear blue skies they were operating in at the time this event occurred now were they?
Not defending the apparent errors made by the crew, but rather encouraging the "after the fact experts" here on this forum to look at WHY the crew might have reacted in the manner they did...
Maybe airspeed unreliable training scenarios should include distractions such as convective weather and turbulence before the event occurs....