Your point is right but my side or opinion about class fields are a new feature in javaScript that introduced ECMAScript 2019.
FACT : This new feature is not yet officially part of the language specification and is not standardized in JavaScript. It is only supported by modern web browsers such as Chrome, Safari, and Firefox. Currently, it is at "stage 3," and it may be released at "stage 4" in the future. It is still under construction and will likely become official in the near future.
Highlight :
Class field as "data properties" and "behavior/method" that declarer and initialize instance variable and contain also instances of class. They published two types such as public and private.