Yeah, that's how I see SBDs...as I do with the USD. I'm not accumulating either one in order to make profits off of holding them. Short- to mid-term, I should be able hold to them and pretty much not lose. But it's certainly not a way to actually gain, given inflation.
To make gains, you'd need to invest those SBDs or Dollars into something with positive returns that cover the losses from inflation. If you're not at least covering that, then you're losing.
That being said - the inflation for USD is typically low enough to make your realized gains relatively easy to achieve.