I don't doubt that some people have had success with the oil immersions and various other break-in techniques. I see these as attempts to expedite the break-in process. As with almost any accelerated process, they come with increased risks. That risk is over softening the leather, leading to over stretching it and ruining the saddle.

Using the traditional method, or one very closely related to it, the risk of permanently damaging the saddle is low. They are tried & true over decades of use. Brooks is likely to play it conservative and recommend a process wherein the odds of damaging the saddle are very low. And they know their process does work.

Even if a more aggressive process was well-known to Brooks, it might be difficult to explain it in such a way that people don't go overboard. Heck, look at the way things are now. Brooks recommends a conservative process but out on the Web, there are dozens of much more aggressive techniques. Think of what people might be recommending if Brooks said to use more oil.

Consider - let's say that the standard Brooks recommendation leads to a failure rate of 0.1%. But an aggressive oil immersion has a failure rate of 5%. Such a case would lead to 19 out of every 20 immersion advocates saying it worked fine for them, and this would true. But it would also be true that their failure rate was 50 times higher than the Brooks way.