As a person with Hungarian Jewish ancestry, I would like to weigh in with an anecdotal story to support these findings.
My father's father as it eventually turned out was fully Jewish. He was born in what is now Serbia, but was Hungary until 1920 .
In 1914 in Budapest he married an ethnic Hungarian who was Catholic. In 1917 they had a child, and a marriage record was produced presumably in connection with registering the child
The document is very interesting.It includes the religion of both spouses. My grandmother was very straightforwardly identified as RK which are the Hungarian initials for Roman Catholic. For my grandfather his original religion had been blacked out, leaving one letter visible, a z, then in a different hand, he too was marked RK. The document also included a promise that any children of the marriage would be raised Catholic, a promise made only when one of the spouses was not Catholic. In other words he was Jewish in 1914, but by 1917 presumably had converted and was now Catholic.
He had two brothers both of whom also converted.Â Â One of the brothers married a Jewish woman and she too converted.They also had a sister who married a Jew and as far as I can tell she and her husband did not convert.Â
My father and his brother were indeed raised Roman Catholic and trained never to reveal their Jewish ancestry.
I only know because my grandmother slipped up one time in front of my mother and referred to her husband as Jewish.
So of this family of three brothers and a sister, who had two Christian spouses and two Jewish spouses, four of the six Jews converted to Christianity. This would be in the period >from about 1915 to about 1925.