You can also just use the computer for the opening. If you don't have a certain opening, or response to a certain opening memorized, just use a computer. The difference between a memorized opening and what a computer would suggest is basically nil.
It probably isn't as helpful to a grandmaster, but that's true of engine analysis in general
Yeah, although at that level lots of people are also getting into good positions, having no idea why it is good, and losing it.