I was concentrating on the choice between were and was (subjunctive vs. indicative), and I neglected to address the choice between was/were and is (past vs. present).
New2grammarCould you please 'defend' native speakers' tendency?
You're referring to the use of past throughout once the main clause introduces the past tense. Hmmm. Defend it? That's difficult. If you're right there looking at the boxes, I suppose
is is just as good as
was or
were. The situation is in present time, after all. I suppose that when the native speaker matches the tenses throughout a sentence, it's a matter of habit, not always a matter of logic. The basic principle is that backshifting is always correct. Not backshifting is optional, and depends on the logic of the situation.
I'm not sure if that answers your question, because I'm not sure there's ever actually a 'defense' for how people use language.
CJ