Should I manually assign Text right after programmatically setbinding it?

[suugbut]

Background

• A custom control Changer has one bindable property Text and 2 buttons:
  • Up (incrementing the Text) and
  • Down (decrementing Text as long as Text is positive). The Down button is disabled when Text is 0.
• MainPage is bound to MainPageViewModel and it has 2 radio buttons:
  • RadioValueA is bound to ValueA of the MainPageViewModel.
  • RadioValueB is bound to ValueB of the MainPageViewModel.

Issues

Consider the following screenshots.

Workaround

Manually assign Text after programmatically set-binding it.

ChangerInstance.SetBinding(Changer.TextProperty, nameof(MainPageViewModel.ValueA));

// Why should I call the following?
ChangerInstance.Text = _model.ValueA.ToString();

Question

Why should I manually assign Text right after set-binding it?
Should it be done automatically by the framework?
Is it a bug or a feature by design?

Repository

Here is my repo: https://github.com/suugbut/dynamic-setbinding-bug