So, the KLM flew at 40,000', above the ash cloud, so their only exposure was in the climb and descent. BA spent a total of 2h45min airborne instaed of their planned 4h, and spent it at varying levels, so only a matter of minutes at the intermediate altitudes that have the highest risk. That invalidates their "tests".
No-one on here supports the apparent lack of investigation into the problem, and no-one wants the restrictions to last longer than needed. However, the continuing view from some that no engine failures means it is safe to resume normal ops is astonishing - given that the company test flights were a con trick, and that numerous military engines have been wrecked, it points to a complete cowboy attitude. Anyone supporting an immediate return to flying should have their licence permanently revoked - you're wanting to play Russian Roulette with hundreds of lives.
The simple fact is that there is not enough data to make an objective assessment whether it is safe or unsafe, and it is that research that is needed, not a resumption to ops because patience has worn out or economics are deemed more important.