Comment by lapcat

Safari supports 3 major macOS versions. For example, Safari 26 continues to support Sonoma and Sequoia as well as Tahoe: https://support.apple.com/en-us/127685

Safari 27 will support Golden Gate, Tahoe, and Sequoia. However, Safari Technology Preview now supports only Golden Gate and Tahoe, despite the fact that the same WebKit commits will make their way into regular Safari on Sequoia. Thus, it seems that Apple is just shooting itself in the foot by failing to test sufficiently on one supported platform.