Now, HMD think they are so great offering 3 years of updates, but look at the first table - 3 years doesn't look very impressive any more does it! As others have said elsewhere on the forum - Lumia devices that are 5 years old are going to get updates until the end of the year, but the 3, 5 and 6 might not get anymore updates at all?
"Dead Nokia is still supporting it's phones but new Nokia can't?!"
is not very good for marketing! HMD have to support the 2, 3, 5, 6, 7 and 8 until the end of this year at least, otherwise old Nokia will still be supporting devices longer than them - bizarre!
As I've said before, HMD should stop comparing themselves to other Android phone manufacturers and compare themselves to the real competition, the "auld enemy" - Apple. (MS would also be competition if they hadn't stopped making phones, as they also supported WP8, 8.1 and W10M for several years).
The second table is even more interesting, as this is where we can find Android phone manufacturers. You will see that it lists the Nokia 6 and speculates that it will get updates for 2.5 years! Haha! We are starting to find evidence that this speculation is unfounded, unfortunately. In general though, in this group, HMD look quite good.
Personally, since Nokia 3, 5 and 6 will be on Android 9 I see no reason why HMD can't provide security updates until Android 9 itself is no longer supported by Google, just like Apple and MS do for their phones and OSes.
I hope HMD do what's right.