In the gradient settings, the Angle in option is only used for linear gradients. Therefore, if the Angle in option is enabled, radial and conic gradients will not be displayed. It is better to display the Angle in option only if the linear gradient is selected. In the other two gradient types, the Angle in option will be hidden.
I understand what you mean and have created an improvement task, as it is not a bug, since radial and conical gradients have no angle value, as you say yourself. Accordingly, it is correct that the gradient is not displayed because the syntax is wrong
We’ve fixed this issue in Bricks 1.9.4, now available as a one-click update in your WordPress Dashboard. However, we have added a new little problem in the process, see: WIP: Gradient / Overlay missing "Angle in °"