Vector API is very far from being hardware intrinsics. Unfortunately for Java programmers, it’s merely a least common denominator of SIMD instructions across different ISAs. This makes the feature very limited by design, IMO borderline useless.
Before this in the OpenJDK the developer had exactly 0 control. You just wrote code and hoped JDK would slap in vectorization etc.
Example: https://news.ycombinator.com/item?id=36624240 The linked C++ code is easily portable to C# because hardware intrinsics, but not to Java because nothing similar to _mm256_sad_epu8 is available there.