Abhorrent but not about preventing marriages, at least not directly
"Can Non-Jewish People Settle In Israel?
Under the Law of Return, it is possible for non-Israeli family members of Israeli citizens to gain long-term residence status in Israel, including spouses/partners, children, and grandchildren, if they themselves are not Jewish.
Where a non-Israeli national is married to an Israeli citizen, they can initially acquire a temporary residence in Israel after six months. With this temporary status, they can then access the social welfare system in Israel, including healthcare. Citizenship is then possible after four years, however, the process for securing this is quite rigorous, as the Israeli immigration authorities want to be assured that the relationship is genuine.
Where a non-Israeli national is in a relationship with an Israeli citizen but they are not married (i.e. a civil partnership), it takes three years to gain temporary resident status in Israel. Permanent residence in Israel is possible after six years (as opposed to four for those who are married). However, those in a civil partnership cannot acquire citizenship, just permanent residency, regardless of how long the non-Israeli national lives in the country." https://immigrationlawyers-london.com/global-mobility/perman...
They will also claim it is about preventing terrorism, but that is an extremely transparent fig leaf.