Kirkt,
Yup you explained exactly my issue. I don't think it's an issue anymore, but I'll share here what I've learned through your answers and a few searches. For ACES to work properly, I need to work with ICC display transform (in my case srgb), convert from Acescg to srgb (linear) using OCIO, then manually tonemap it using curves. I was trying to avoid using luts or curves for tonemapping, but that's exactly what it needs. I just wish AP had an easier way to do it. Like in Davinci Resolve you just set your working color space, set the IDT and ODT and you are done
Here's the exr file if you still want to take a peek: https://drive.google.com/file/d/1m5MC9O7JMjB3UKLCSgIAwKoA9v84UuWe/view?usp=sharing