It's right, they have no distinction, because they used the verb "устать", which is literally like, "to become tired" rather than an adjective like us.
Because of that, if you wanted to express what you're expressing, you'd need the pluperfect tense ("I had become tired", rather than the perfect, "I have become tired". "Had you become tired?" is logically equivalent to "were you tired?" in every case except if you were born tired lol)
Russian has no pluperfect, they just use the perfect for that. So therefore you would use the perfect in all cases, and it's probably better to translate as the perfect case. If you want the equivalent of pluperfect, you can qualify with a specific time. e.g.
"were you tired last night?", "Ты устал прошлой ночью?" is logically equivalent to the pluperfect, "had you become tired last night?", so you can express pluperfect with time qualifiers instead.
It is consistent. "ты устал" is the correct translation for "are you tired", and "were you tired".
In English, "tired" is an adjective. When you ask "are you tired?", you are asking "are you in the state of having exerted enough effort to the point of becoming tired?"
In Russian, "устать" means "to become tired", it is the process itself of exerting the effort. So when you say "ты устал?" you are asking, "did you exert enough effort to become tired?", which - depending on context, can mean you are presently "tired" as we'd say in english, or you were tired previously.
So "Вчера ты устал?" - "did you become tired yesterday?", aka "yesterday were you tired?". Russian Whereas if someone has literally just climbed a hill, "ты устал?" means "did you become tired?", aka "are you [currently] tired?". There is no pluperfect in Russian so you can't make a clearer distinction.
Having said that, Russian also has the adjective уставший. It would be abnormal phrasing, but you could technically say, "ты уставший?" and "ты был уставший?" and that would mean "are you tired?" "were you tired?", with no ambiguation.
So... because this verb means "to become tired" instead of "to be tired", as English would assume it, the ending is tricky? Since вы can also be formal, does вы устал also work if speaking to a singular person?
Does this also mean that there is no distinction in meaning in the Russian question "Are you tired" or "Were you tired"?
Usual not-a-native-Russian speaker disclaimer:
- "Did you become tired?" = at the past time to which we are referring, were you tired? (referring to something that was or was not true in the past)
- "Have you become tired?" = at this time, are you tired, have you become tired (and are currently tired)? (referring to something that is or is not currently true)
They don't mean the same thing, so it makes sense they might not both work as translations for the same Russian sentence. You're not comparing like with like.
All this said, I can't for the life of me remember or figure out how one would take the Russian idiom for expressing tiredness (which would literally I guess be a past tense of to tire), which is already past tense, and put it "further in the past" to expressing having been tired at a previous time.
Edit: I went to Google translate, just to see, and it suggests a past participle, which makes as much sense as anything else (and the participle in question feels vaguely familiar). I am tired - я устал, I was tired - я был уставшим. However, double check with an actual native before relying too heavily on the combination of my memory plus Google translate... Especially since right now, я очень устала 8-o