Angles entity keyvalue doesn't take into account "angle" (yaw only) keyvalue.

[Bluespark99]

If an entity has an angle keyvalue (and doesn't have an angles value) then its yaw will be determined by angle which isn't reflected in the angles keyvalue which is displayed in the default entity attributes window. In this case angles always the inferred/default 0 0 0 value unless explicitly set in the entity. This means that unless you check all your angle-sensitive entities in Raw Edit mode you may miss the true yaw angle and instead see the misleading 0 0 0 value in Angles.
If angle keyvalue is parsed in the entity then that keyvalue should either be displayed under Angles as an additionaly keyvalue or the angle keyvalue should be transposed to the yaw of the displayed Angles. Or some other solution.

[wootguy]

Doesn't that behavior depend on the game? This additional angle key should be added to whichever FGD you're using so that you can see it in the Attributes tab. Linking keyvalues like this can cause confusion especially if another game implements the angle key differently.

Edit:
It doesn't depend on the game, and the engine uses "angle" value even if "angles" is present. It overwrites the yaw in angles if set to a value greater than 0. If -1, it replaces angles with "-90 0 0". If lower than -1, it replaces angles with "90 0 0".

I don't want to link the keyvalues, but this combination of angles will be shown in the 3D view and a warning will be shown if the selected entity has an angle key.