Like UIProgressView, MDCProgressView‘s accessibilityValue is based on the current value of the ProgressView’s progress property. Also like UIProgressView, this accessibilityValue takes the form of a whole number percentage. To ensure the same behavior between the two classes, the MDCProgressView class has a static UIProgressView that instances query for its accessibilityValue whenever they need to provide their own.
The ProgressView announces a new accessibilityValue whenever its progress changes if VoiceOver is on.