I understand what Taylor Stevens meant. While I don't think there was an official policy of marrying within races, it did happen, and there certainly was a racial strategy and ethnic policy of sorts, and there certainly was racial stereotyping. Most of this was unofficial and intangible, but definitely noticeable if you cared to look. Unfortunately, I don't have the time or inclination to try to remember or look up all the references (most of these have been purged from their documents anyway) for what I am about to assert here, but I know that I have looked into this enough to state it with certainty.
Berg subscribed to, and TFI still subscribes to a racial hierarchy that looks something like this:
Jews are at the top, because despite their having rejected Jesus, yada yada, they stem from the chosen nation to start with. Many leaders such as Shem (and Zeal) were praised with references to his Jewish ancestry. They were/are praised for their brains, skills with money, leadership and management. Even though Berg hated Israel, he made a thing out of Jewish ancestry, and anyone within the ranks with Jewish blood was usually highly respected as long as they played the Berg-ass-kissing game.
Caucasians, the sons of Japheth, with their biblical ordination to rule over the houses of Shem and Ham were at the top. I can think of many examples where leadership positions were given to Caucasians despite all the talk of nationalization. Caucasians were the ones with the real power on the field. If "locals" were ever given leadership or authority, they usually had to be paired up with a Caucasian either through marriage or a co-leadership position.
Latinos were given a lot of leeway but seen as temperamental and in need of discipline. There are many examples of Berg letting Latin leadership have their way until they "blew it" and needed straightening out by Caucasian/Jewish leadership.
Asians (sons of Shem) were never really trusted with too much, especially Asian males. Asians were seen as pagans in need of Christianization and in constant need of training due to having very little background in judeo-christian values. Asian females who were paired up with Caucasians were given positions of authority, but generally Asian couples or couples with Asian males were not.
Africans, the sons of Ham, were mentioned (all ML references have been purged, unfortunately) as stemming from a cursed and troubled race. It helped to be African American, but they were seldom trusted with much authority or responsibility.
I don't know which race or ethnicity was/is at the bottom of the totem pole, but I do know that Caucasians were at the top, and the cult was a distinctly American export. For a long time, white Americans were seen as the only viable representatives and purveyors of the anti-establishment hippie culture that Berg wanted to spread to the rest of the world. This carried on well after the hippie era was over, and I would be surprised if it still isn't that way today. The socio-cultural domination, i.e. the leadership and cultural flow, was from white America outwards to the rest of the world. In other words, you wouldn't find an Asian national going over to run important operations in the USA, but you would find an American overseeing publications operations in Taiwan run by locals for the sake of security. In many instances you would find ideas of mixed marriages being pushed, because it looked good in terms of nationalization. If an all-Caucasian couple requested a separation, it would more likely be granted than for a mixed couple, who would be pushed to stay together no matter what, just because it looked "good" and fit some idea of theirs about racial harmony and grooming local leadership.
TFI began as and remains a distinctly racial organization. Although globalized, it is distinctly an American cultural export, with white American leadership at the top and mechanisms to ensure their continued dominance.