The rule is as you state it: if the condition still appertains now, then the present tense is also possible. I say 'also' because the natural tendency of the native speaker is to regress the verb of the independent clause. That is why it sounds more 'natural' in past tense.
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purveyor"I never knew that you have such a callous heart."knew and thought in the main clause are almost never followed by a subordinate clause in the present tense.