Saying that building one 10-minute Gran Turismo track takes the same amount of work as building four 3-minute tracks is like saying that if a builder can construct one large house in a year, they could have built three smaller houses in that same time.
That sounds reasonable at first if you're only looking at the total square footage, but that's not how construction works. Every house needs its own foundations, site preparation, utility connections, permits, inspections, planning, and project management. Those aren't things you do once and then get three houses for free. You have to repeat them for every separate house you build.
Track development works much the same way. The length of the track is only one part of the job. Every individual track needs its own layout design, terrain work, scenery, landmarks, AI racing lines, pit lane setup, timing sectors, optimization, testing, bug fixing, and countless polish passes. A lot of that effort is per-track overhead, not something that scales directly with lap time.
So if you compare a single 10-minute track to three separate 3-minute tracks, you're not comparing one big project to three thirds of a project. You're comparing one project to three projects, each with its own design, implementation, and testing requirements.
The total amount of asphalt might be similar, but game development isn't just laying asphalt. That's like judging house construction purely by floor area and pretending foundations, plumbing, permits, and inspections don't exist. The reality is that three separate tracks often require significantly more work than one longer track because so much of the effort has to be repeated for each one.