The fact that you have to research court cases to answer these basic questions shows the problem exactly. I'm not a tax lawyer and am just a blogger. The conservative approach would be okay if there were some automatic means of following it. Such as with Bitpay and Coinbase where our Steem Dollars automatically converts to Bitcoin the instant received.
Steem Power also has a lot of other issues too so when you research consider the fact that the developers still have centralized control over Steem Dollars. At any time the developers can decide to change for example the vesting period as they have done in the past to make powering down slower or faster. So we don't even have assurance when we will be able to access by powering down let alone what it will be worth once it reaches our bank account. It's an accounting nightmare.
You are absolutely right, the IRS has some work to due and owes us an explanation. At the same time, Steem made these currencies complex even more so than standard Bitcoin trading. That fact that I have to go beyond basic publications/code/regulation to explain the treatment is ridiculous, but I think it will be necessary to have the most informed path, until the IRS can catch up.