Playing devil's advocate
Being of an analytical mindset, technical folks can tend assume that their performance primarily will be judged based on a scorecard of completed vs committed requests, but in practice, it's not as cut and dried.
Before development even begins, customers start to form opinions on a team's performance based on their level of confidence and willingness to commit.
Part of the reason for this is that customers can have a difficult time assessing whether a contractor's hesitation to commit is due to the sheer difficulty of the request or lack of ability of the contractor.
As there are no absolute criteria for measuring difficulty of a request, often what is more important to the customer is trust that the contractor is giving 100% effort, rather than whether 90% or 100% of the requests are met.
Suppose the customer has to choose between two scenarios:
Contractor A:
- Confident they can deliver on all requests
- Result: 90% of requests delivered
- Customer is pleased that the contractor gave 100% effort
- Customer perceives that the uncompleted requests were due to unforeseen issues, which probably outside of the contractors control
Contractor B:
- Commits to delivering on 90% of the requests. Not confident they can deliver on the remaining 10%
- Result: 90% of requests delivered
- Customer is disappointed that the contractor didn't try to complete the other 10% of its requests
- Customer assumes that the uncompleted 10% of requests were due to either lack of effort or ability of the contractor
In both scenarios, the same number of requests were delivered; however, the customer felt that the "overcommitting" Contractor A was giving 100% effort and used this to validate that the remaining requests truly were difficult, to Contractor A's credit.
On the flip side, the customer felt like Contractor B wasn't giving 100% effort and its inability to complete all of the requests was either due to Contractor B's lack of effort or ability.
Disclaimer: I am not advocating overcommitment as a strategy; this is just an observation of a possible real world situation in which overcommitment might have positive results.