If Udyr uses the elixir of skill before lvl 18 he will have an additional point when reaching lvl 18, but if he uses it while being lvl 18 he will not get an additional point.
From the League wiki...
Notes "Elixir of Skill does not increase the champion's level nor does it allow you to gain skill points beyond your champion's maximum, which is 18 for all champions except for UdyrSquare Udyr. The additional skill point is granted only if it's used before level 18, including on Udyr."
Seems like they know.
