inheritedStyle property
The default text style in force where this widget sits — what the theme was offering here, including for the fields the widget overrode.
The third column of the merge, and the only one not derivable from the other two. textStyle says what won and properties says what the widget asked for; neither can tell "you set 13" from "you set 13, and it was already 13". An override that changes nothing is a line of source that could go, and that is a thing a design system wants told.
Ambient, which is not always the same as inherited — see styleReplacesInherited. Empty for everything that draws no text and for every reader outside the app.
Implementation
final Map<String, String> inheritedStyle;