This is wrong. Why should it be a person? Only "something tall" should be accepted.
When we see these adjectives used as nouns in the accusative, could we also translate it, for example in this case, as "something tall"?
Why not valamit magas? Wouldn't the adjective go back to being an adjective and then would valami not need to be a noun in the accusative? I feel like I'm missing something here...
Adjectives (like magas is), usually get -ak and -at ending when using low vowels, in contrast to nouns where it's mostly -ok and -ot. It's weird.
I think some back-vowel words (with -a/á/o/ó/u/ú as the final vowel in the stem) get -at as an accusative suffix instead of -t or -ot.. Maybe because it flows better in speech?
Then again, I'm not an expert, so I can't say for sure
I agree. As a native english speaker, I would never say "a tall one", and I would have no idea what someone meant if they said "a tall one". I think "a tall person" and/or "something tall", depending on how Hungarian speakers use it.