I'm pretty sure Catalan was made official before 2006? The Constitution of 1978 recognises Castilian Spanish as the official language of Spain, but also allows for co-official languages if the autonomous communities so designate them. I'm not sure of the year, but I'm pretty sure Cataluña would have very quickly afforded itself Catalan as a co-official language.
The problem with your claim is that the Spanish government didn't count catalán as a language. It wasn't even really considered a full dialect until recently. The co-official language of Cataluña was English. Also, to further the problems, valenciano is a whole other entire dialect that is barely getting its due recognition at the moment. It is not the same as catalán. You would severely get an earful from either region claiming they are the same.
I've lived in Spain for many years and in fact I was in Barcelona during the elections last year, so I'm sure catalán was NOT an official language. This year was also the first year there was an option for those that wanted to to take university entrance exams and exit exams in catalán, because it was finally made official last year.
Sure many people speak it, but it doesn't make it official. Spanish in the US is only an official language in Florida I believe, even though there's up to 80% hispanic population in several border states and where Spanish is a dominate language over English in many cities.
Good luck with your visa application and all that stuff. It will be a long and painful process, but just have lots of patience. You'll get use to it all sooner or later. Just don't stress out about it. The Spanish don't.