https://en.wikipedia.org/wiki/Greek_language_question
So regardless of whether there's a "true" Basque language, it certainly could have gone through a period of conscious, top-down reconstruction after some period when middle-class academics (and politicians, usually) who would be interested in either rediscovering or purifying the language, or just plain looking for a nationalist project to rally around couldn't find anyone left who spoke the language at all, spoke it purely enough for them, or even spoke it prettily enough for their image of what the language should be.
I don't know that this happened to Basque, but it happens all the time.
Standard spanish is used all around in the sense that: people have known it for a long time. We understand it all. Of course there are localisms, but the same way Andalucia, Extremadura or Murcia speak a very strong dialect, in my area or Valladolid, Salamanca, Madrid or even Cataluña people speak a very standard one. In fact, the areas you said are the most "dialectizied". The rest of Spain is way more standard when speaking it.
Pero no me informo por canales políticos exclusivamente. Sé de lo que hablo, créeme.
Las diferencias entre euskalkis son como las que puede haber entre un murciano, un chileno, un cubano, un colombiano y un mexicano. El léxico puede variar enormemente, incluso las conjugaciones verbales auxiliares (dot/dut/det) pero el idioma es el mismo. En castellano pasa igual con dile/decile al otro lado del charco en el cono sur.
Sobre el uso político, para mí portugués y gallego podrían ser el mismo idioma perfectamente salvo diferencias morfológicas triviales, cosa que ya ocurre de forma clara en la conjugación verbal argentina, chilena y uruguaya.
You can believe it or not. That is not to say that it is not the local language of that area. But they make it look like it was the only, true one, when this has not been the case for centuries. The same valencian was the original in my area. But it was mixed with castilian (what you know as spanish is castilian) for centuries.
What happens nowadays is that they force and do not let people study in spanish in some areas. Spanish have the right to study in the language that they deem appropriate from the official ones in their area. And so that you see I am not inventing anything, because people will jump to me it is not true. It is in fact true that for years there have been people who cannot study in spanish at school in the public system, a few days ago we even had in Mallorca a resolution from judges that denied the right for a student to study in spanish!
Here, catalans denying 25% of teaching in spanish ignoring even court resolutions: https://elpais.com/espana/catalunya/2022-05-31/la-generalita...
My first gf when I was young had to come to my area because she was denied the right to study in spanish in public school. This is not a joke, it happens all the time for years.
Here a student that cannot (has not the right, according to judges) study in spanish, when it is a guaranteed right. This shows the politization of the court system, bc it does not exist in the law, no matter their twisted argument, a denial of the right for a person to study in an official language in that community (county equivalent), yet it is happening: https://www.elmundo.es/baleares/2022/11/14/6372645121efa0721...
Here basques trying to kick out spanish from the education system: https://www.lavozdegalicia.es/noticia/espana/2022/09/18/gobi...
This is a topic where they typically say (the nationalists) that since spanish is everywhere they should be able to deny the right to study in spanish, bc they will learn it anyway. I am all for letting people to study in basque, catalan , valencian (which I can speak also) or what they choose.
I am, at the same time, totally against the public system forcing you to choose one of the languages they decide.
This is continuosly used with political goals.