The guidance didn't single out miners at all. Anyone who provides a service of converting bitcoins to fiat and vice versa is considered a money transmitter. A miner or individual who converts their mined currency to fiat using an exchange or spends it for their own purposes is not a money transmitter.
Yes, it did single out miners - or at least that is the thinking among the compliance professionals (lawyers and non-lawyer compliance experts) that I work with. The relevant language is:
"[a] person that creates units of convertible virtual currency and sells those units to another person for real currency or its equivalent is engaged in transmission to another location and is a money transmitter."The consensus is that "persons who create units of convertible virtual currency" are miners. Moreover, the guidance did not explicitly limit the "money transmitter" label to those miners acting as a business. Note that it uses the term "person" not "business" when it describes what miners must register. Personally, I believe you are right, and if you read my thread, you'll get a more in-depth explanation of why. Nonetheless, I believe we are in the minority there.
Looking at the second instance of the term "person" I wonder if a miner who sells his bitcoins on an exchange, a business instead of a person, is defined as a money transmitter.
Similarly, I wonder if someone who pays a kid to do yardwork using bitcoins that he himself mined is a money transmitter.