Depends, there are billable hours e.g. time spent with customers and non-billable hours e.g. administrative tasks not specific to any customer such as payroll, transfer of knowledge between work colleagues. So by targeting reduction of non-billable hours, you would have a compelling reason to sell to firms who bill by time.
That's pretty much true in general. Our fees are dictated more by the market than our actual costs. So if we were billing fewer hours, we'd just raise the hourly billing rate for our associates.
From our perspective in the national standards group, we would actually want our associates to just spend more time on value added activities. Instead of wasting time organizing PDFs of exhibits and monkeying around in spreadsheets, we want to them evaluating the relevant legal and technical tax issues. So it's not precisely cost control that is the primary concern, but quality assurance.