Unless there is a definitive reason between defining a hybrid vs a big turbo (or simply non-hybrid turbo), such as construction is different, method to make power is different, different technology, etc.
We're just using terminologies based on preference.
I'm not sure what criteria Turbo Technics used to label the S280 as a hybrid turbocharger. How does it differ from a non-hybrid turbocharger?
If it merely comes down to preference, then in the context of this FiST platform at the very least, it's been universally understood that a hybrid is just a stock kp39 modified like it's on steroids.
Anything else that doesn't rely on the stock kp39 is a new (big) turbo.
For people that are either new to this platform or new to turbo upgrading, understanding there is a distinct difference in characteristics between a hybrid and a big turbo is valuable. And it helps to preserve the simplicity of:
hybrid = stock turbo, quick spooling , less top end power, lower power ceiling, runs hotter, absolute direct bolt on, etc.
big turbo = completely new turbo, slower spooling, more top end power, higher power ceiling, runs cooler, might require slight or a lot of modification, etc.
Maybe there is some overlap, cause the S280 is small and shares some "hybrid" characteristics. That was the selling point for me, but I also understand it's technically a different turbo altogether, which is also the selling point for me. In this context, I wouldn't want people to get mixed up calling the S280 a hybrid like it's a X47. Because the characteristics are different.