And I used the termed line of sight specifically, although I guess it's synonymous with ground wave.
No, line of sight and ground wave are not synonymous. They are distinct modes of propagation.
Although a gross oversimplification ground wave can be seen as RF that creeps along the ground, and so can follow the curvature of the earth. It goes out and follows the earths surface past the visual horizon.
Sky wave is, naturally, RF that departs the source antenna and reflects off a portion of the ionosphere or something high in the atmosphere before being received. It goes up before it comes down someplace..
Line of sight means you have a direct path, essentially visual path (not limited to human visible wavelengths of light), from your antenna to the other antenna with no obstructions. Trees, buildings, etc, don't count in this case as obstructions to the "visual" path until the frequency of operation is high enough that the RF cannot penetrate (see through) the "obstruction".
You can be in line of sight and also be in ground wave (you can also be in line of sight and in sky wave), but if you are in line of sight and no ground wave (or sky wave) is present you will still receive the signal, assuming the signal is leaving the source with enough ERP, in your specific direction (taking into account things like radiation pattern), to overcome free space loss and deliver a signal sufficiently above your MDS.
In actuality even with no sky wave and no ground wave you can (and often do) still get propagation beyond the visual horizon. Scatter and refraction will bend a line of sight signal to some extent. The Radio Horizon is most often something beyond the Visual Horizon, even at frequencies taken as truly line of sight limited. I can't count the number of times I have seen an I or J band (J band is up to 20 GHz) radar track a target that was just behind a hill and not visible, or was well below the curvature of the earth for the geometry.
I'll leave the argument of "is aircraft scatter sky wave? Or is it line of sight with scatter?" to someone else.

T!