I agree and I'd add to it. You could do this as 25/5, 50/10, 90/15 or whatever else. The key thing to me is to single-task during the time period (work on one thing in an undistracted manner). Also I'd add to get up to a maximum sustainable level of single-tasking on hard things (ala Cal Newport's Deep Work).
Work for 90 minutes then take a 15-minute break: https://www.powerofpositivity.com/researchers-explain-take-work-breaks-every-90-minutes/ .