you can build a to do list app in a handful of minutes if you know your way around
No you can’t. You’re mistaking a “hastily thrown together prototype”, for an “actual app” with all its requirements, tests, multiple target support, hundreds of tiny features, QA for all that, then deployment, and ongoing support.
Depending on where on the scale between “prototype” and “final product” you look at, it’s going to be anywhere from less than an hour, to a full team working for years.
Now, arguably, showing whether you know the difference, can be the real test.