I’m not convinced that was the correct assumption on their part. Hermaphroditism isn’t an aberration in my mind, it’s survival mechanism. It’s obviously undesirable from a quality-uniformity standpoint, the good you mention, but it’s an indicator of a more diverse gene pool. If the biologist is trying to create an IBL tomato for example they’re after uniformity a farmer can borrow money for, an absolutely predictable product. A good example of the risk of that is the several occurrences of blight on potatoes. Something that had a chilling effect on my personal genetic background.
Imagine a disease or significant shift in weather like an ice age (an extreme example) that in a particular location decimates a population and perhaps for some reason it only effects males. The ability of dioecious plants to reproduce in individual isolation allows the continuation of the line. As we select away from that we move from diversity to homogeneity and we end up with enormous but bland beefsteak varieties that travel in trucks well but taste like acidic cardboard.
I don’t consider hermaphroditism an evolutionary eddy or vestigial expression like an appendix.