Security updates for R340 branch

According to this knowledgebase article support for the R340 branch of the drivers extend through the end of 2019. Yet the R340 branch hasn’t recieved a security update since February 2017, and there has been 5 security bulletins (1, 2, 3, 4, 5) for the newer branches listing critical issues that doesn’t mention R340. Are we to assume none of these issues affect R340? Or is the support for R340 bullshit?

Now take this into account:
So, theorizing that R390 will be a new legacy release it will die by 01.19 while R340 wil last until 12.19. Makes sense. And looking at other support documents for supported features on different OSes makes it even weirder.