There are a couple things to consider here.
First, in a modern or futuristic economy, backed currencies are absurd - for example, there isn't enough gold in the world to reinstate the gold standard even if everyone wanted to, and trying it would implode every economy in the world with massive deflation. As such, the energy-backed credit is a laughable regression from fiat currency and is prone to wild, unpredictable fluctuations in money supply. For example, someone (even someone in another empire) building a dyson sphere, much less several civilizations building them, would dump so much energy into the economy as to create a hyperinflation crisis due to how abundant and cheap energy becomes.
Second, fiat currency is awkward as a gameplay mechanic, and even in real life, much less in video game, can encourage gamey monetary policy because the money supply is literally just some numbers on a spreadsheet.
Third, some sort of galactic standard currency is also weird, and while it wouldn't allow players to pull crazy modern monetary theory nonsense, raises the question of why the fanatic purifiers and xenophobic isolationists use the same money as anyone else? And gestalts wouldn't even have a concept of money.
My overall opinion is that energy-as-currency is moronic in any sensible analysis, and if anything, the idea of having to worry about having enough "money" in a interstellar empire with any decent, modern (much less more advanced) understanding of economics is actually kind of weird. If a specific currency must exist as a gameplay value, energy sort of as a mechanic, but it creates a lot of oddities, like the idea of trade, an energy-consuming task, creating energy or "buying" it from nowhere, as well as having robots that literally eat money.
