Recently, I got into a brief argument with a colleague when I mentioned that I wanted to use an engine playing against itself to generate a larger sample size for a rare sideline.
His argument was that human chess and computer chess are two different things, which made sense. Humans don't scan for every possible legal move, and don't use brute calculation like computers do.
However, there may not be a time when masters decide to play a given line, meaning that rare lines would have fewer games played. There would be no other way to build a larger dataset other than playing games yourself or waiting for other people to play it.
Another factor to consider is how seriously people take TCEC openings.
Is the difference between humans and computers substantial enough to dismiss opening testing with an engine playing against itself? Would the use of computer games be a flawed sample size for determining the validity of a move?