Many of us use them. Lighter weight. Helps shake any excess flour you may accidentally pick up with a solid peel.
Solid peels work too. It's not a must, but they work great.
NOTE: don't be leaving them in the Blackstone too long or the aluminum will warp. I mean like 15-20 seconds. This really isn't an issue for most because, in reality, most oven time by a peel in a Blackstone is in the 3-5 seconds range