I assume lawyers have some mechanism like this already. Law firms can require staff to allocate every 6-8 minutes of their day. Which sounds terrible and likely to be wildly inaccurate as people cannot be bothered to invest that much overhead into their job.
This is how Swiss medical appointments are billed. I forget exactly how granular, but it's pretty small - 5-10 minutes. As a result, you tend to be quite efficient when going to the GP, because it’s a few Francs a minute
If I retain a lawyer at $1k an hour, you bet I want 5 minute billing.
In my experience it just means a lawyer marks each hour via charging you 10 increments, and that in some cases some forms of comms are generally charged at a sub-hourly charge.
In most cases working with a lawyer is a fixed fee or going to be on a retainer basis where the hours pile up regardless, not so much about tracking every moment for every person.
For sure that seems the intention. Create an “audit trail” for billing while simultaneously making it so onerous that the employees have to fudge the numbers.