For agile teams one of the most used metric is whether teams complete all work that they committed in iteration planning.
There is no wrong thing about measuring whether an agile team can adapt to complete all work committed. However we cannot expect them each time to achieve their goals and complete all planned work within an iteration. This is not realistic. In fact this kind of expectation and pushing, get the team to commit a bundle of work that can be done easily.
Excessive and huge expectations can lead dysfunctional behaviors.
These dysfunctions, sometimes come out as a commitment to a bundle of work that they don't believe to be able to complete, and sometimes they persistently keep themselves in a comfort zone with achievable works.
In both extreme cases there would be some setbacks. Sometimes predictability goes down, motivation and self-confidence of teams are affected, and sometimes innovative approaches become blunted.
For this reason, it needs to be very careful and looking for a good balance while setting up dates and goals.
Agile teams should aim to complete all of the work they planned in iterations in 80% of their time. In terms of predictability, it is a better way instead of expecting teams to overcome the impossible. I'm not talking about finishing 80% of the work they planned, that's a different case. To be clear, a good and well determined team is expected to complete all work they predict in 8 out of 10 sprints they run.
However, It might be difficult for teams that frequently interrupted and work in a very complex environment. In an environment that urgent response frequently needed, it a lower success rate should be aimed. Of course, you need clarity to distinguish what really needs an urgent-response, and also need to be firm and resistive about it.
So in a well-structured and enabling environment, for well-designed and cross-functional teams which have compelling directions, as supported well to overcome impediments, do 80% predictable work. If not you should look over and check all the parameters that is mentioned in this sentence again.