If...big if...it's really a quality stainless steel, it should be perfectly fine in terms of being inert and non-toxic. I have a couple of these and find them to be among the best algae cleaners I own (glass tanks only!). But...a pot-scrubber is something most people think of as a cheap disposable item, so I really doubt that they are using high-grade stainless in their manufacture. Mine attract a magnet pretty strongly; I suspect that they are the lowest grade of steel that can still be legally referred to as "stainless".
They don't hold together very well, nowhere near as stable as a plastic pot scrubber. After only a few uses they start to unravel and come apart and require more and more careful handling as time passes. If used as mechanical filtration media they would be a royal PITA to handle and clean. If used as biomedia, along with an efficient mechanical pre-filter, they might be okay. The strands are very flattened and ribbon-like, so they look as though they might have way more surface area than a standard plastic pot scrubber with its round filaments...but I'm guessing here, and the toxicity question remains.
They don't hold together very well, nowhere near as stable as a plastic pot scrubber. After only a few uses they start to unravel and come apart and require more and more careful handling as time passes. If used as mechanical filtration media they would be a royal PITA to handle and clean. If used as biomedia, along with an efficient mechanical pre-filter, they might be okay. The strands are very flattened and ribbon-like, so they look as though they might have way more surface area than a standard plastic pot scrubber with its round filaments...but I'm guessing here, and the toxicity question remains.