Mainstream supports means no more features, but it's still getting patches, I imagine.

Nope.

"End of support refers to the date when Microsoft no longer provides automatic fixes, updates, or online technical assistance. [...] you will no longer receive security updates"

That refers to the end of extended support, which just recently happened for Windows XP. Vista is under extended support until April 2017, as mentioned on the page you quoted from.

I think Microsoft is deliberately confusing there, but that's referring to the end of extended support. Extended support means only security fixes (and fixes you pay tons of money for).

Scroll down to the table on this page: https://support.microsoft.com/en-us/gp/lifepolicy