Any actual thoughts on why RA is not a suitable reference for the call? airbus might be wrong...
If you're taking off from
Courchevel's airport you are guaranteed to get a positive rate from the RA even if you're actually descending instead of climbing. This is an extreme example, but there are plenty of airports out there where the ground falls off rather sharply after the runway threshold, thus making RA readings irrelevant for the purpose of establishing whether the aircraft is actually climbing as opposed to the ground just dropping off more or less sharply.
Ciao,
Dg800