Agree, hands on is great and it's an awesome way to learn. Anything that gets hardware in to more hands is positive. However, limited programming of a third-party hardware platform is a far cry from learning "mobile robotics" in any intellectually honest sense, which was my original point. Useful indeed, but a small part of the overall equation.
The grandparent obviously has limited experience. Custom electromechanical systems, particularly mobile ones, are not like software. You can't spitball them together in five minutes for free, and you can't build more than a tiny percentage of things using ready-made parts if you care about weight/space/cost/repeatability/efficiency/etc. Particularly if you are planning to take them to market and want a defensible USP.