I think Bobby was mainly focused on the work to the greens. Neither his father or brother touched them and he seemed to feel that the installation of the PrecisionAire system and re-shaping of the greens was erasing history instead of what could be considered restoration.
So in effect, Gil is mowing down the Ross greens and replacing with his interpretation of them, based on photos from a golf program. At least that's what I took away from Bobby's statements. I suppose he feels work to the greens is different than work to bunkers, fairway width, mowing lines and tees.
Do renovations erase history? Yes. Flynn erased history when he renovated Macdonald's Shinnecock, Ross erased history when he renovated Essex County, Tilly erased history when he renovated Baltusrol, and so on. It's a different course after the work, some times it ends up better afterwards.
Renovations have been going on since the dawn of time yet what seems to change is the stated purpose behind them. Up until recently, it was ok to renovate for the sole purpose of making the course better, without much regard for what existed before. The last few decades, however, have moved to something else. A course undergoing work is returning to something in the past more often than not. It's still a renovation and it's still erasing history, but it's under the guise of erasing a more recent iteration of the course to return to an earlier one. Sure there's nostalgia built into it but I'm not sure that's necessarily a bad thing to some degree. I'm also not sure whether a second Golden Age and Nostalgic Age have to be mutually exclusive.
Gil did say about his work at Oakland Hills that I think relevant here and I wonder whether Bobby had read or heard, “we’re undertaking a restoration of the South Course at Oakland Hills. Donald Ross did the original, of course, and it was Robert Trent Jones who did the renovation that created “The Monster” Ben Hogan conquered in winning the 1951 U.S. Open. Rees Jones later revised his father’s work. The plan is to restore kind of a hybrid of the Ross and Jones designs, the best elements of each. The course will be closed for nearly two years beginning in 2019, but when we’re finished, without a doubt it will be a Monster again, albeit one a little different than the one Hogan brought to its knees.”
I played Oakland Hills South last month and while I was not able to play the course before Gil's work, I was taken aback by how good it was. Whatever you want to call the work and to whatever extent history was erased, they have a remarkable course currently.