Udyr is a top tier duelist, absolutely. He is not, however, a top tier LATE GAME duellist. The only way I would 1v1 at 6 items with the above is if I built like full Chad 1v1 Udyr and they build teamfight Jax.

Udyr is a monstrous mid game duelist. Warrior Trinity completed by like 17-18 mins? Forget about it, he will melt anyone or anything at that point in the game.

Late game? Udyr typically will not have great arpen, no true dmg, no scaling % hp damage, so he's just doing flat AD.

I will win 1v1s versus Jax Fiora if I outplay late game, but it's just not doable on equal skill footing, with both having 6 item 1v1 builds.

Typically in higher elo too, it is tough for jungle to compete with top lane farm. Plus, a 6 item Udyr built to 1v1 is pretty bad in late game teamfights. A 6 item Fiora with the full damage build + GA? That's going to wreck.

Udyr (warrior tiger) does 1 thing really well. In early, mid, and late game, he will completely annihilate squishies. And he will kill turrets really fast. That is pretty much it; late game I'd much rather be on a Jax for better duelling, better catching ADCs, better CC, more tanky with ult. But at 20 mins with my 2 item spike? Udyr will wreck anyone unless they are more fed or more skilled.