This is a structured version of something Coach Ryan Kohler prescribes to athletes preparing for off-road races where there will be variable terrain and the need to control the effort over a long duration.
The aerobic strain is high since the workout involves riding a tempo effort over a long period of time, and the small sprints at the end of every block provide an added stimulus to replicate surges that may be required on uneven terrain or in a race scenario.
Overall, you will learn to deal with variation in your effort while maintaining a high aerobic output over an extended timeframe.
Coach Kohler stresses that this is a great workout when your primary objective is building the aerobic engine—in the middle of the base phase or early in the build phase. The sprints aren’t so hard that they will leave you tanked, and they provide enough of a strain on the body that they make a fun way to break up a long ride.
Kohler also notes that you could incorporate this workout into a long base ride leading up to an event as an event-specific session.