Estimating: similar to planning, thinking through the whole problem and surfacing early anything that seems like not a big deal on the surface, but actually is.

Estimate changes over time: surfaces underlying issues e.g. too many urgent bugs/fires/triage, product changing priority constantly, etc...

Yeah, I don't think "seeing how estimates change over time" is very valuable. The reason that "planning is everything" is that it makes a problem tractable.