those studies are a bunch of nonsense, usually based on tiny samples that don’t represent the majority of patients.
They also assume that eclampsia/preeclampsia is purely an immune problem, but the syndrome has several variations...and is more common in areas where people are malnourished or high risk: women having first babies have a higher rate, as do women with high blood pressure or with twins.
But I had read that one of the reasons why women having ther first babies suffer from it at an higher rate, is that they have not had much exposure to their husband's semen before their pregnancy. (For instance, I had a C-section for PIH, and I had gotted pregnant just 6 weeks after our wedding.) Women who use condoms as a contraceptive before they become pregnant, also have a higher rate of preeclampsia, and possibly for the same reason: the condom prevents contact with their husband's semen, and thus they have not had the frequent exposure which is protective by lessening the risk of a preeclampsia immune reaction.
Or so they say.
OTOH, I was also told (this was 24 years ago) that not getting enough protein during pregnancy was a risk factor, and I was encouraged to try for 100 g protein daily. Man, that's a lot of protein! --- and, as I mentioned, I still developed PIH, resulting in the doctor's recommendation of a C-section (and he was a conservative, as-natural-as-possible OBGYN who had a reputation for resisting C-sections unless there was a clear indication.)