Does the dialect you're taught affect perception?

[StrangerCoug]

I am a native English speaker and was taught a seseo version of Spanish in middle and high school. I know for a fact that many places in Spain have distinción and pronounce soft <c> and <z> as [θ] instead of the [s] I'm used to, yet when I listen to somebody with such an accent, the [θ] is something I have to listen for despite that sound being in my English dialect.

A similar phenomenon partially affects modern Greek. I know <δ> is [ð] (again, a sound my native English has), but if I'm not paying attention it'll sound similar to its classical pronunciation of [d], which isn't helped by the way modern Greek names are transliterated. (Interestingly, I correctly perceive <β> as [v] consistently—it will never turn into in my head.)

Is it just me here? Or do other people also perceive dialectal sounds as other sounds despite the ability to distinguish and pronounce the original?

[Yng]

there might be something to it - definitely when you get good at a language, you stop noticing distinctions present in your native language and start applying allophonic processes naturally, so you maybe don't pay attention to the exact quality of two allophones of a vowel (which are distinct in English) or in my case, don't notice whether someone is pronouncing /T/ as [T] or [s] (because it's not really distinct). I think a more likely culprit the fact that you listen for words you already know and you have a set idea of how they're pronounced in your head which might not line up exactly with what you hear, as well as the fact that modern Greek [D] might well be pronounced in a way distinct from your English /D/, for example (possibly with features that your brain wants to interpret as English /d/ rather than /D/).