Earlier quoted context omitted.
QQQ is up 5x in 10 years. Being an ETF, that means many of its components must be 10x. I suppose it's dependent on your time horizon. MSFT is up around 10x since Nadella took over. It's more common over 20 years, obviously.
The other neat thing about ETFs is that there are so many similar, you can effectively use them for TLH to help offset future gains.
I'm not an IRS agent and have no idea what they mean by substantially similar. You might want to talk to your tax accountant.