I know Engage doesn't have the best writing but can we agree this is just ridiculous?

We know Sombron impregnated female dragons left and right in the past to produce many offsprings, he certainly didn't care about the feeling of his mates, and we can assume that he only impregnated females of the dragon kind (instead of human) to ensure that the offsprings' draconic power isn't so diluted. So, why on Earth he hasn't done it to Zephia then? Her Mage Dragon's bloodline is likely more superior than regular Dragon's bloodline (like Veyle's mom), she has been loyal to him for ages, and she didn't look too bad on the eyes, not to mention she also wanted to make babies with him anyway.

What do you think of her writing for this particular scene? My headcanon is that she's infertile because if she isn't then she would've done it with male humans too since she eventually accepted some human as part of her family anyway.