Very well done! It took me 17;17 on my run. All the mechanics are intuitive and you do a good job of introducing them throughout and building upon each. I died 46 times total, but none of the times felt unfair. The minimalistic style is also extremely well done, looks nice, and is very effective. It's always clear what will kill you and what you need to do.
I can see that point. That section was indeed the hardest albeit that section's placement late in the game and the frequent saves you provide justify the difficulty. So, I would say it was more difficult, but not conceptually unfair, although I could see how some players might think that way.
Also, another note: I liked the one gem that you provide a peek of before the player falls down a chasm and then suddenly sees later in the ascent. That was clever.