As it turned out, the signals derived from such indicators were misleading and the recovery in GDP growth did not materialise. Note in particular how the PMI, that will turn out to perform well in the 2005-06 period, wrongly signalled an acceleration in activity for the first few months of 2004. As you see, relying on € would have suggested a more bearish conclusion.
In particular, while at any point in time one can always find an indicator that closely follows GDP developments, it is not the case that this happens consistently through time for any single (elementary) indicator. On the other hand € has always performed remarkably well in terms of tracking growth.