Not all grammar rules are logical, and different languages have different rules (and different logics). The best explanation probably is that every language evolves following its own path. I know it's not very helpful.
And you're mixing up two different things here. Vthanhtrung's first question was why there is no future tense in adverbial clauses of time, his second post was responding to your request to give an example of an adverbial clause in the present or past tense. He gave you examples of the present tense.