While listening to the 1st book of Robert Caro's LBJ biograph series on audiobook I opened LBJ wiki page and found claims that he had helped secure visas and done other work to help Jews escape Germany and resettle in Texas (https://en.wikipedia.org/wiki/Operation_Texas).
I haven't gotten that far in the book yet but this article(http://www.aish.com/ho/i/Operation-Texas-LBJs-Mysterious-Mission-to-Save-Jews.html) claims Caro didn't write about it and my impression was that Caro's biography's were supposed to contain just about every important incident in LBJ's life. Is there not enough proof this actually happened? Did it happen or was it just a rumour?
This article was published in 2009, and seems well sourced, with many sources published in the 80s and 90s.
Volume 1 of Caro's autobiography was published in 1982.
It's quite probable that Caro's biography will have some gaps or be contradicted in places by later scholarship uncovering important details. No author writing history, even one as respected as Robert Caro, will have the absolute last word on a subject for generations. I wouldn't be surprised at all if he missed some details on certain subjects. However, Johnson's well connected string pulling on behalf of oppressed people is kind of consistent with Caro's depiction of Johnson's character, even if Caro does dwell rather more on his darker side.