You're overthinking it and in fact AWS has a bunch of security stuff (HSM, secure enclave, etc) that makes it extra attractive. For reference, Stripe (which isn't FTX but it's Fintech and handles large amounts of money) uses AWS for their environment. If you're asking if there's some secret hidden AWS region FTX was using, why would they bother? The known special region, GovCloud, is a couple years behind the other regions in features. Also from what's been publicly revealed, FTX isn't exactly the shining example of the finest possible engineering.
https://aws.amazon.com/solutions/case-studies/stripe/