There's no way to prove the second partition is real encrypted data instead of random garbage. It gets wear-leveled but that would also be the case if the true

There's no way to prove the second partition is real encrypted data instead of random garbage. It gets wear-leveled but that would also be the case if the true partition had been resized before. It doesn't matter if the false partition is unlocked or not - you can plausibly deny there's anything on the phone at all.