Questions: Can you upgrade Boost/Setback Die? If so, under what circumstances?

Sources: Page 295, Core EOTE. "... Note that boost and setback dice are not normally upgraded to other die types..."

Page 11, Core EOTE. ".... Setback die are not as potent as Difficulty dice...." Boost and Setback are thematic opposites of one another, therefore one can assume the boost die is not as potent as an ability die. Therefore, Boost and Setback die ( if they can be upgraded) would be upgraded to ability and difficulty die respectively.

Comments:

1. Even if you can upgrade them, I can't imagine there are too many instances where you could even utilize this rule. If you are aware that you can, could you also provide examples of when would be good times to upgrade them and how to?
2. I looked at Google, FFG, Errata, and also looked at the book to see if the question was already asked, and I did not find anything related to the question.
3. The way it is worded (not normally upgraded) suggests they can be. Poor wording, or intentional? No where else in the book do I see it mentioned, especially not on pages 10-11 or pages 20-22 (explains the dice and upgrading/downgrading/increase/remove)

No, you can not upgrade them. Probably just poor wording or an attempt to leave it open to future adjustments pending splats and expansions.

However, saying that a circumstance that would normally add a number of Setback die is dire enough that it should instead increase the difficulty by a number is not unreasonable. The benefit to having a difficulty die rather than a number of Setback is that there are talent that remove Setback. So if a circumstance is dire enough, making it a difficulty die prevents characters from reducing the difficulty. As the GM, you are the arbiter of the difficulty level, and don't need to go through this many steps. Easy enough to just raise the difficulty and then add Setback as appropriate.

I wouldn't use this though, I would just add Setback and/or possibly upgrade Difficulty to Challenge.