6% in a currency that was inflating 6-9% each year (the comment you were replying to was almost certainly referencing USD, which has recently inflated at a little under 2%). The real rate would've likely been no more than .5% on those accounts, and probably negative some years. Does dai inflate at 5.5%+ per year?
Not necessarily. Our equivalent to a savings account (caderneta de poupança) had a return above 6% per year until a couple of years ago (it's down to slightly above 4% per year now). It's very easy to beat that (for instance, the 5-year prefixed federal government bond has a return of 6,39% per year at this moment). So a return of 6% per year would be considered normal around here, not a red flag.