To the Ukrainians’ dismay, there was a crucial departure from what Ukrainian negotiators said was discussed in Istanbul. Russia inserted a clause saying that all guarantor states, including Russia, had to approve the response if Ukraine were attacked. In effect, Moscow could invade Ukraine again and then veto any military intervention on Ukraine’s behalf — a seemingly absurd condition that Kyiv quickly identified as a dealbreaker. Russia tried to secure a veto on Ukraine’s security guarantees by inserting a clause requiring unanimous consent.
With that change, a member of the Ukrainian negotiating team said, “we had no interest in continuing the talks.”
Maybe find an article that says that then. The one you linked says that yes, they were close to an agreement, but at the last minute Russia inserted a clause that was a dealbreaker
That is a very strange article. The headline is "How Boris Johnson Sabotaged Ukraine Russia Peace Deal In April" and the bulk of it is about how a former US National Security Council officer didn't say that.
Frankly the NYT one seems a lot more convincing to me. That addition to the security guarantee clause is obviously completely unworkable.
Obviously things you want to hear seem more convincing to you. There are however statements from Ukrainian negotiators where they confirm the change of direction in negotiations after western interventions. I've done enough looking things up for you here, but feel free to look them up on your own.