It's about the label.
They're using "staking" on their platform and the crypto includes bitcoin. Not everyone understands the whole thing about stake/POS or it's just that when a word is being used, there's an exact meaning based on its use.
Well, I'd just remember that even though it's somehow not really a technical stuff.
To be fair, the word "stake" and "staking" didn't even originate in proof-of-stake or cryptocurrencies in general. "Staking" could simply just mean handing over your stake. "Stake" being a word also being used in the financial markets in general.