True, but they own some of it, and there is competition between platforms for them (I.E. lyft vs uber). In fact many people "work" for multiple platforms. It's similar to a farmer selling his ware in a marketplace, which he must pay rent for. Would you say that because he doesn't own the marketplace (or store) he doesn't own his means of production?

Now the question is whether they must own all of the means of production to be considered bourgeois? I would say no, especially in today's world, where most production is a complicated multi-tiered process.

But even if you do think so, they are still much better off, Marxist-wise, from virtually every service worker, who own no means of production.

In any case, that doesn't mean that there is no exploitation or that the gig economy should not be regulated, but it really doesn't have anything to do with Proletariat.