The job this tool does, and who does it today
Ask a sales manager how quickly their team responds to new enquiries and you will usually get a confident answer. Ask how that answer was calculated and the confidence drops. The number typically comes from an impression formed by watching two or three reps on a good day.
Where measurement does happen, it is usually one person exporting a form log and a call log into a spreadsheet at the end of a quarter, matching them by phone number, and producing an average. That average is then presented, disputed, and forgotten. Nobody trusts it because everybody can name a lead that was handled in four minutes and another that sat for a week.
A lead response time grader's job is to produce a number people believe: median time to a human attempt, split by source and by working hours, with the tail shown rather than averaged away.