As per the lifecycle support link
" Updates are cumulative, with each update built upon all of the updates that preceded it. A device needs to install the latest update to remain supported"
Windows 10 lifecycle currently gives a specific date limit, no reference to build number.
The last statement is quite clear, only Build 1607 is supported, no other previous build is supported as of the release of 1607.
Nothing unusual in that, Windows 7 lifecycle gives an end of support as 2020 but ONLY with SP1 installed
So all your previous build are not supported NOW.