Boeing "thrust hold"

[slamer.]

This is something I have pondered on for some time and in light of events surrounding Asiana 214 at KSFO yesterday this seems like a relevant time to ask.

I understand what happens when the is AP is disengaged in FL change (or other vertical modes depending on type) and auto-thrust goes "HOLD". And the subsequent requirements with FD use.

What I don't understand is. Regardless of the procedure, why would the manufacturer philosophically want "thrust Hold" at such a critical phase of flight, potentially without any reversion.

Or to put it in simpler terms .. what were the people who designed this mode thinking..?

The FCOM usually provides the answers. But in this case .. not.

PS

I have asked people in our ATO. And even had a quick searched here without success.

Thanks