Most of the defi apps that have interest on stablecoins depend on the price of the yield token, ergo the interest is subject to daily market conditions in crypto.
HBD has a relative fixed 10% interest defined by the witnesses. It can change yes, if most of the witnesses decide so, but in general is far more secure then then most of the defi apps.
Now we need to make it a bit more stable :)
I think this will be the case when the DAO/DHF has a lot of funds, 50M plus and can handle large daily volumes.