Not an expert by any stretch, but I *think* that Matt was trying some tricky play where he’d announce his spell, presumably Nature’s Claim, then crack a number of Chromatics as mana abilities to pay for it. Normally you tap mana then play a spell, but you can also announce the spell then pay, but there’s really no reason to do one over the other.

The problem is that you cannot “overpay” for a spell. You must pay the exact cost, that being CMC +/- any taxes or reduction effects, and can’t pay more. You can float as much mana as you like, but any mana that is unused for the spell just sits in your mana pool. For a spell with X in the cost you still don’t overpay for the spell, you just pay the cost and however much X you want. I don’t have any idea what Matt was thinking or any idea why he wanted to try it, and I couldn’t find a good explanation anywhere. You are right, he didn’t need to go through that judge call and could have just won.

Post sideboard the most common hate players have for KCI is graveyard hate. My understanding is that KCI reduces its reliance on the graveyard and the Retriever loop to compensate.

KCI is a very complicated deck, the only advice I have is practice until it’s rote memory, and even then don’t assume you know everything that could happen.

That was the finals of GP Las Vegas, and it’s the moment I was referencing. Matt clearly knew that he couldn’t actually go off that turn and was setting up to make Yuri pop the Stone so he could potentially go off later, and Yuri did nothing. He clearly didn’t understand what was happening and didn’t read Matt’s pauses as cluing him in. Whether Yuri could have won the match is another matter, but he definitely shouldn’t have lost that turn.

In fairness to Yuri, it was the finals of a GP. Exhaustion and the pressure of being under the lights were certainly factors and may be the real explanation. However, I’ve seen the exact same thing at local events.

Recently I watched Matt Nass play against an opponent in a top 8 match. It may even have been a final.
What I saw baffled me. His Tron opponent had an oblivion stone on the battlefield. He had the mana to activate it. Matt took his turn and the first few things he did (spells, abilities etc) he deliberately paused and gave his opponent credit for knowing when to crack the o-stone and disrupt the combo. His opponent did nothing. Matt kind of physically stuttered a couple of times, in surprise I guess, as he was allowed to just enact the combo and build an unassailable position.
By the time his opponent decided to crack the o-stone it was too late and didn’t do anything at all. At the highest level of play in the finals of one of the biggest tournaments on the planet, Nass’ opponent made what looked like an FNM-level rookie error.

I backed up the footage and watched it a couple of times, too. I wanted to watch it from the Tron player’s perspective and see if I missed anything. Nope. I’m flummoxed haha. There was a definite clear moment where cracking the o-stone denies Nass the ability to go off that turn, but i guess the Tron player just wasn’t familiar with the deck or was exhausted from a day of playing. Either way, with the removal on-board and the mana to use it, he just handed Nass the game. It was a little strange to watch but then I had to check myself because just like that Tron player, I’ve made similar errors in my time and all of them are circumstantial and forgivable.

Still. I thought it was worth mentioning.