Good find there! After wondering about IRQ performance on Arduino ESP32 for quite a while I luckily came across this. Yes, same in Arduino ESP32, my map file shows my IRQ in flash. I opened a ticket with the devs which was answered quickly: https://github.com/espressif/arduino-esp32/issues/11977

..they think that ISRs in Flash are safer. But there's also a suggestion at the bottom, I haven't looked into that one yet though.

Thank you again for your work, I might just switch to ESP-IDF from hereon.