Lua(La)TeX 没有对连字符后的自由字符进行字距调整？

Question

\documentclass{book}
\usepackage[usenglish]{babel}
\usepackage{fontspec}
\directlua{
    fonts.handlers.otf.addfeature {
        name = "testkern",
        type = "kern",
        data = {
            ["O"] = { ["f_f_i"] = 500 },
            ["f_f_i"] = { ["c"] = 500 },
            ["r"] = { ["fl"] = 500 },
        },
    }
}
\setmainfont{Latin Modern Roman}[RawFeature = +testkern]
\usepackage{showhyphenation}
\usepackage{showkerning}

\begin{document}
Office\par
Official\par
Butterfly
\end{document}