Did I say mandatory? I meant optional! You’re “free” to die in a cardboard box under a freeway as a market capitalist scarecrow warning to the other ants so they keep showing up to make us more!
If you wanted to receive Bitcoin, it would be an investment. The taxable income would be the value on the day I received it. The value on the day that I sold is irrelevant. This is not “unrealized gains” by any stretch.
Then someone better tell the IRS because this is exactly how they treat crypto. And yes, people can elect to be paid in Bitcoin, I recall seeing various stories about it over the years.