They push the belt to the side.
You're right of course, but I think the deeper issue is that crash dummies and tests are designed just for the "average" and that many people fall outside of this "average". As a 2 metre tall bloke I've sat in many cars where the head rest just doesn't raise high enough for example.
So the thing is that the issue of female crash dummies is a special case of the wider "crash tests should represent a wide range of people". Of course women of various shapes and sizes should be included in that, but also men of various shapes and sizes. By focusing so strongly on only specific groups (women in this case), I think sometimes these larger issues get kind of lost, even though the specific focus isn't really a bad thing in itself.
You can suggest testing a wider distribution of crash dummy types without also inventing a scenario in which this article somehow prevents that from happening.
One problem is that tackling easy causes of male deaths is met with complains about making men softer or feminizing them.
For example you mention incarceration and studies show a "sentencing gap" where if a man and woman commit exactly the same crime, the man will on average receive a longer sentence. But there is no call to reduce incarceration for men specifically. There are some calls to reduce incarceration for everyone. There are also bizarrely some calls to reduce it for women specifically in the name of "gender equity" (even though the "sentencing gap" already privileges women).
Basically it's politically incorrect to specifically help men unless you wrap it up in language about how it actually helps the people who matter, i.e. women and children.
The world is complex, and when dealing with groups of people even more so.
https://www.nhtsa.gov/nhtsas-crash-test-dummies
Presumably the difference here is around weight distribution and other limb length and size proportions. Still I think "First Female Crash Dummy" is a stretch.
But honestly, dont see issue. Men are loosing nothing in this. Male dummies will continue to be used too.