Are there any other Advantages than this to a special Macro lens compared to just a macro tube with a lens?

There can be and usually are.

Most macro lenses are highly corrected for field curvature. The point of correcting for field curvature is to give the lens as flat a field of focus as possible. If one is using a macro lens for reproduction work of flat works of art or documents, for instance, this is an important feature. Many other lenses do not have as flat a field of focus. Some lenses, even very expensive ones, intentionally do not even attempt to fully correct for field curvature.

Only pinhole cameras and theoretical 'zero thickness' lenses have a perfectly flat field of focus. Every other simple single element lens starts out with a field of focus that is a portion of a sphere. As corrective elements are added for various aberrations including field curvature, eventually the field of focus of a highly corrected lens can resemble a lasagna noodle: It's basically almost flat, but there are undulations across the field.

Non-macro lense designers usually also attempt to render as flat a field of focus as is practical for the lens in question. Part of how much is practical for a specific lens is the target price of the lens. Lower priced zoom lenses are usually more concerned with price and other image quality characteristics than they are with a very flat field of focus that can be very expensive to do, particularly across the various focal length ranges of zoom lenses.

But there are also reasons why uncorrected or undercorrected field curvature can actually be desirable in a lens. The main one is that such lenses can demonstrate very smooth out of focus areas, sometimes referred to as 'smooth bokeh'. Lenses that highly correct field curvature tend to have 'busy' or even 'harsh' bokeh.

If you are going to use extension tubes for macro work and desire uniformity of sharpness and focus distance across the entire frame, it's usually best to begin with a fairly well corrected prime lens (a lens with a single focal length) rather than with a zoom lens.

Another consideration regarding extension tubes is that their effect with regards to overall magnification is based on the ratio of the tube's length to the lens' focal length. A 25mm extension tube will increase magnification by a much larger ratio for a wide angle lens than for a telephoto lens. For example, a 25mm extension tube will double (+100%) the effective distance between the optical center of a 25mm lens and the imaging sensor. That same 25mm extension tube will only increase the effective lens to sensor distance of a 250mm lens by 10%.

For more about how a lens designed for macro work might different from a lens of the same focal length designed for portrait work, please see: Why is the Tamron 90mm 2.8 marketed as Macro and not as a "portrait" lens?