Ether Fund vs Ether?

I'm in Canada and invest in Ether using Wealthsimple. In Canada, we have what's called a tax free savings account (TFSA), tax free investment vehicle up to a certain amount. You can't put Ether in your TFSA. However, there's an ETF on Wealthsimple called The Ether Fund (QETH.U). I've also put money in to that, but a lot less. I thought QETH.U would track Ether's growth, but it doesn't. For example over the last month, the Ether Fund has grown 56% while Ether has grown 75%. At that rate I might as well pay the tax on Ether! Does anyone know the reason for this?