This seems to apply to 4.4; according to https://www.kernel.org/category/releases.html 4.9 has not been extended, so it only applies every few years that there will again be six year support.
If, as per the table below [1], they've already moved on to 4.10, then 6 years is a long time to support 4.9
[1] https://android.stackexchange.com/questions/51651/which-andr...