I am no expert, but to me the debate is the same as switching from gendered pronouns to saying "they". I try not to use "he" or "she" in my documentation now. I say "they" or "the user". I don't do this because I have dyed hair and a nose ring. I do it because it is an incredibly easy to do and removes gender from the docs. That's it. Gender adds no information in technical docs most of the time and has the potential to bias information. I don't even care that much about this issue but it is just easy to do. No one is confused by this or even mentions it.
So, say we start using main and secondary. Someone smart enough to be reading a datasheet will probably figure this out. Right? I work in several different programming languages in any given week (SQL, C#, JavaScript, various data formats, and so on). I don't get confused when the name of a data type is a little different between these.
I am not trying to be rude or mean, I am just saying we can change terms. I mean, my god, we changed from Imperial to Metric while I was in elementary school. We changed an entire system of weights and measures for an entire country (Canada). That was a big deal.
Going from master/slave to main/secondary (or whatever) is not a big deal.
It's like "rule of thumb". I no longer use this phrase. Most people have no idea that this is based on how a stick a man may beat his wife with must be no thicker than the size of his thumb. But some people do. I do. And, yeah, I am sure this will be a "turns out" where a cabal of feminists spread this rumour to make white men feel bad, but I don't care. I don't say it any more. I figured out a new way to talk about a general guideline that is widely applicable and simple.
It's not a big deal.