That's total nonsense, you have to make it larger to include a charging mechanism (which would need to be proprietary to fit) and it's more difficult to manufacture in a water-tight way. They're spending significantly less on developing and building this than Oura has. Keep in mind Oura has raised over a billion dollars in funding.

The e-waste here is negligible. If you've ever tossed a laptop or phone you've effectively produced more e-waste than a lifetime of these little things. A single disposable AA battery is more waste by weight.