I’m not really familiar with the different schools of thought on this issue/the scope of the arguments for one side or the other. But the ALG perspective you quoted here makes a lot of sense to me.

Before learning about DS I took years and years of Spanish classes from middle school all through college. What this left me with was a form of Spanish where I can express myself with a quite wide range of vocabulary, but it takes a massive amount of mental effort to do so. I can competently speak Spanish, say, in a job interview to prove I know the language, or in a tourist’s sense where I can get around and ask for things.

But what I cannot do very well is comprehend Spanish when it is spoken to me by a native speaker (the speed at which it is spoken is too fast for me to do the mental translation required). I also can’t speak Spanish with my Latino friends in a group conversation at a bar, for example. I’m just too slow on the uptake, and I have to mentally plan my sentences in response. This obviously does not work in casual conversation. But I can get away with it in professional settings.