Global Bond indices: Justification for weights

But what is unknown are interest rate developments and future yields, affecting today‘s bond prices.

Bonds going up during stress periods etc.

Term premia etc.

The quote is only really true for single bonds held to maturity imo.

Not really, it also apply to ETFs. If you have AA grade/y maturity bonds from 10 issuers, you’ll get the same result as if you had from 20.

While for stocks you don’t want to miss those stocks that go to the moon.

From that point I agree for sure.
I maybe misunderstood here.

I was refering to different maturities/credit etc. and for example going long constant maturity long bonds, and subsequently harvesting term premium.

Individual bond issuers agreed here, it‘s very straight forward.