Your own description of your work seems self-contradictory?
You have a paragraph that says you could work much faster than others and still "finish them with accuracy, attention to detail" and then in the very next paragraph you note that going so fast meant you were making mistakes and overlooking things.
This is only to say that I'm not sure how to interpret your own description.
It also sounds like the KPIs that had been set did not match the stated goals of your supervisors. KPIs focused on speed of output while your supervisors are telling you that quality and attention to your work is more important. I see this as a classic example of an organisation falling into the trap of just measuring what's easy to measure because they can't measure what they actually care about.
The KPIs weren't focused on speed at all; don't know how you came to that conclusion. Their KPIs were in-line with their spoken criteria and they were always calibrating for best outcomes.
The only time speed or volume was at issue was when we had a backlog. Sometimes we would begin to miss deadlines/time frames and sometimes there was priority work to be picked up. And AFAIK, KPIs weren't looking at those as a negative. It was just one of those productivity issues we encountered in staffing vs. amount of work vs. deadlines.
Basically my work was excellent by all objective criteria and I was receiving fantastic performance reviews. But I still had room for improvement, don't you see? Simply because of the high rate of speed, I could personally tell that it could've been better, more, nicer, with some TLC and some better pacing. That doesn't mean that anyone else noticed or cared. It was mostly my personal assessments of how I was doing.
But they did drop hints -- once or twice, an issue was raised and my mentor said "It's easy to miss if you're going quickly lol". It was just a hint and hardly even criticism, just a reminder that slowing down wouldn't hurt.
And it's true that the rewards weren't there. If I finished everything then everything was finished and sometimes I was forced to clock out without work to do. That was the drawback of hourly wages for, essentially, piecework.
Slowing down was fraught with complications. I type 100wpm, my thoughts operate at a certain pace, and I would get into a groove like playing a video game. Would you slow down in a video game to do a better job? If I slowed down, would I do better or would the artificial pace cause trouble? I often tried playing ambient, tempo-less or downtempo music to slow my pace, but I would typically just find a rhythm and go with it, rather than artificially slow down. Honestly, due to physical issues and the whole WFH distraction, it was often difficult for me to stay at my desk for a stretch.