It is nice to have some flexibility within a 401k to reallocate what goes where. My wife had something similar with the oil and gas company she used to work for. However, we did not realize or begin to exercise the flexibility they offered her to move investments around until around the last few months of the 17 years she was employed there. I know, that's sad. We did not even think to look into her 401k flexibility until we had serious threats of oil stocks failing the end of last year due to oil prices falling.
Yeah, it is good to attempt to be proactive, when you can, and I had a similar situation for like the first 6 months of one of my investments, and I thought that I had sufficiently allocated within the fund.. and I guess I had made a mistake and got confused about it. Lucky I caught it after about 6 months, and was able to reallocate in a more diversified manner.. My investment was pretty low during those first 6 months anyhow, so it didn't really make any kind of major difference in the whole scheme of things, but it could have made a major difference if I had not caught it for 6 years or something like that... hahahahaha
A lot of her 401k was company stock. It was given to her automatically every month by the company. Since her company she used to work for was in oil and gas, fluctuation in oil prices also affected her company stock price. If we had known about the ability to sell all of her company stock and put it into other investments, we would have moved it to those other investments when her company stock price was at $92 instead of doing it when we did at $57.

We could have had another $80k approximately in her 401k.