But, outside of tech, the meaning of slave did not changed one big. I did not seen "master" anywhere except master slave relationship (whether history or bdsm).
So I find theory that calling these two master and slave is unrelated to historical slavery implausible. People who use it first time being inspired by that seems most plausible origin of that name.
While I don't agree with the position that the word "slave" be expunged from tech for some putative role in trivializing historical slavery either, at least the argument does have a plausible premise. The anti "master" crowd though is laughably ignorant of language.
It's still obvious that the modern use of the master/slave combo comes from centuries of slavery, not from any prior meanings. As OP said, that can be shown by studying their meanings outside the technical context. The original meaning was retained in Academia but merely as jargon. Magister artium is a "master degree." There is no "slave degree", though. There is also "mastery", master/apprentice, and so on.
In other words, the offensive component of the combo is "slave", not "master." You can safely continue to use the master/apprentice combo.
An arbitrarily chosen quotation: “ M. le Comte Benedetti, French Ambassador at Berlin..sped to Vienna with the latest proposal of his master.”
Certainly, this ambassador Count Benedetti was not a slave.