I feel like it's pretty clear that gig economy jobs don't neatly fit in either of the existing categories of workers: they're not quite employees (you can clearly work or not work whenever you want) or contractors (you clearly have very little negotiating power or information in choosing your work or guaranteeing your wages). Attempts to munge them into one of those categories are just doomed; a new category is neede…
You can work only when the platform routes a job to you, not “whenever you want”. It's on-demand temporary work with a faster “job is available, do you accept it?” cycle than most, but the general idea of such on-demand work as regular W-2 employment has been around for a long time.