What I look at first isn’t whether your face has fat, but where the fat is
With ONDA microwave, what you want to reduce is the jowls, yet what you worry about is the area under the cheekbones going hollow. In general, fat-reduction treatment can leave the cheeks hollow. With good treatment design and more careful technique, though, this can be avoided; I put extra effort into keeping the face from hollowing, so there is little need to worry. The way to avoid it is to separate these two places and not handle them with the same answer.
The cheek just under the cheekbone is one of the places where hollowing tends to appear earlier. If there isn’t much fat there to begin with, I won’t reduce it actively just because the jowls or double chin look prominent. Improving the lower face doesn’t mean doing the same thing to every area that has fat.
Two fat patterns, two different approaches
If the fat is concentrated mainly in the jowls and double chin, with only a little under the cheekbones, I keep the area under the cheekbones and avoid reducing it too much. What really needs treatment in that case is the part of the lower face that carries more fat.
If there is already a lot of fat under the cheekbones, there is no need to preserve it by default. In that case the fat under the cheekbones can be reduced actively. It still has to be judged separately from the jowls and double chin, rather than making one decision for the whole face.
So whether you can slim the jowls and whether to reduce under the cheekbones are two different questions. If the lower face is your main concern, you can also read how I judge ONDA for a double chin. ONDA joules are the energy accumulated over the whole session; how to read the total and its allocation across areas is covered in how to read ONDA joules.