The software engineers are taxed as they code. It's called salary. Even if they are paid in stock they might be taxed on the value of the stock (complex rules apply).
Employee software engineers sure, but that wasn't my intent with the example. I was thinking more along the lines of independent software engineers working on a new project. In the case of employee programmers, the company creating the software is again not taxed on the value of the software as it's created. They're taxed on the profit when they sell it.
However, if you are mining on a pool you are not really creating bitcoins, you are providing a service to the pool and being paid a fee (usually in bitcoins) based on some formula related to the quantity of service you provided. This is a lot being an employee or independent contractor. The IRS rules are less goofy in this case, though I doubt this was really their intent. Sort of a goofiness-reducing accident.
Agreed that this does complicate the issue. However, it is also akin to a group of people working together to create something, as in the software engineers above.
Bottom line is their "solution" seems inconsistent with the definition of property, and entirely unnecessary. Miners mining for USD profit will sell their coins, and the tax value will be captured at that time.
The issue gets a bit worse with the current weird combination ruling. Generally, capital losses cannot offset ordinary income (except a small allowance per year). So, if you're taxed at the high value when you mine, and later sell the coins at a loss from that value, it may take a long time to recoup the overtaxation. This is exacerbated with the odd montage ruling on mined coins.