Are stainless steel hose clamps safe?

[Lemeshianos]

Have you ever seen a chiller unit for marine aquariums that the heat exchanger (metal part that comes in contact with saltwater) isn't made of titanium?

Nope.
Stainless steel no matter what grade it is, will eventually corrode. Maybe in a month, in a year or a few years, but it will corrode.

However, there are people that dropped screws and other metallic parts in their tank never to be found again and didn't have an issue with their livestock.
So I wouldn't worry that much about a steel hose clamp only if I knew that I would put it on my checklist during the monthly maintenance.