This rumour is apparently mostly false:
First and foremost, Ashley is incorrect in saying that the 1070 Ti can't be overclocked. This is not true. Manual overclocking will be allowed by end users, but from what we can see, there is actually an "overclocking frequency cap." This however does not seem to be what we would call a "low" frequency. If you took a good GTX 1080 and overclocked it, and good GTX 1070 Ti and overclocked it, the GTX 1080 is still going to squeak out a win, but not by much. This is obviously being done to keep the GTX 1070 Ti from cannibalizing the GTX 1080 market. This GTX 1070 Ti should be able to easily handle Vega 64 as well, not that you can find any of those for sale at MSRP anyway.