The problem with the first phase of an engagement
The data collection and cleansing phase is largely unbillable in value terms even when it is billable in fee terms. It is also the phase most likely to overrun, because it depends on client responsiveness, incomplete contract repositories and finance extracts that do not reconcile to agreements.
Clients rarely value that effort, and consultants rarely enjoy it. Compressing it changes the shape of an engagement: the diagnostic conversation happens against structured evidence in the first weeks rather than in the second month.