Not so.
The Sabers in Korea had 50cal rounds that HIT but failed to blow their targets apart. Many a mig returned home with a huge freaking hole in its wing, tail, fuselage, or "insert part here". The 50cals HIT, but due to the tough-as-friggin'-nails Soviet jet construction, the planes could withstand almost anything.
Consequently, that is why later US aircraft began carrying cannon.
Also, the 50cal incendiary round could penetrate a large steel plate with ease. There was a post long ago on the forums that had detailed info about that, and a picture profile of a 50cal round doing so. Can't be arsed to search for it (was 3+ years ago, probably gone)