100%please
Clearly a situation where knowing what the other guy is going to do will increase the probability of a safe outcome, but why would ICAO stick to the status quo?
My guess is that they still consider it more expedient in a case such as your own for the Spanish controller to use Spanish to an EC reg, as do I.
FWIW, my last airprox involved a lack of co ordination between 2 APP controllers in the UK, both talking English, just not to one another.
ICAO even mandates for States who do not use the National language by requiring them to agree a language for aeronautical use, so in Wales you would be talking English as that is the language required to be spoken by the ground station for aeronautical communications.
Glad you lived to tell the tale!