The other question on that transcript is that it appears that ATC is calling out to MH370 at 01:01:19 and it doesn’t respond for 7 minutes and then when it does it just repeats an earlier transmission.
Then at 01:08:00 ATC calls out to them again and MH370 never responds.
Then 10 minutes go by with no response from MH370.
Then at 01:19:24 ATC tells them “please contact Hu Chi Minh City”.
I suspect that ATC suspected a problem and if they didn’t they should have.
And I also suspect that there was no signoff at 01:19:29 — period. That claim is pure Malaysian fiction to cover their rear ends for not acting on these suspicions sooner.
You are correct. That exchange would never pass muster as a radar handoff. Normally ATC would ask the aircrew to “squawk flash” prior to a handoff.
As I thought about this, I’m surprised to see just “MH” being transmitted. Keep in mind I’ve been away from controlling for a few decades but I would expect to hear “Mike Hotel 370” or “Malaysian Heavy 370”. I’ve lost a great deal of my hearing because we had the radios turned so loud to try to understand what was said, so probably the radios are much clearer now and there’s no need to use phonic call signs.