Guide points don’t create lines that can help the Arc Tool to create a tangent arc since there is no line to which it can get an inference.
Guide lines cannot act better than guide points.
You need real lines or edges to allow the Arc Tool to infer a tangent. However, the Arc Tool is programmed to delete the two tangents since it is often used to get rounded corner. This automatic deleting saves you a step.
In your case, if you want to keep the two edges, you have two choices:
1 - Redraw the two edges after the arc is created.
2 - Create a group with the two edges before creating the arc. Then they won’t be erased once the arc is done. If needed, you can explode the group afterward.