From the books I've read, my personal experience and as well my recent samples bear some proof Thin oils, no matter what kind are used to soften and condition the leather because they can flow more easily through the leather, heavier greases and waxes are more for water resistance, protection from the elements and such That's why we add a bit of NFO or whatever oil after we finish working then after that any other heavier greases or waxes depending on the intended use of the product. Boots for example are treated differently than a purse. A purse may need more nfo, mink, mineral or lighter oils to soften it and make it pliable while boots need less of those and more water proofing.
Leather hasn't changed and the products used on them haven't changed, just the way they are sold and who sells them. The leather doesn't care which you use and the oils are even more uninterested.
Back on topic lol. I'm both a broke dude and a cheap old geezer, but feibings nfo products are all that are sold in my lil town so that's what I buy.