Undocumented use of the `BoldFont` option? about unicode-math HOT 5 OPEN

BoldFont works with \mathversion[bold], in cases where all the math formula should be bold not only the alphabetic symbols.

from unicode-math.

@khaledhosny Thank you for the reply! Are you saying that the bold font specified by BoldFont is only used when the \mathversion{bold} is invoked, and will not be used with commands like \symbf?

from unicode-math.

Exactly (and \boldmath which I think is a shortcut for \mathversion{bold}). \symbf switch to the Unicode bold math alphabets, so works only on characters that have encoded bold versions.

from unicode-math.

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{XITSMath-Regular.otf}
\setmathfont{XITSMath-Bold.otf}[version=bold]
\begin{document}
	\[ a = b \]

	\[ \symbf{a = b} \]

	\[ \symbfit{a = b} \]
	
\mathversion{bold}
	\[ a = b \]
\end{document}

from unicode-math.