Hello,
because in i2c_api.c are not any changes between families (exclude STM32H7), then it is possible to compare it with any STM32 target (exclude STM32H7), I think.
I did a test with Nucleo-F303k8 and RPI3 in 2020. I do not know anything about Rust, but maybe you can try to reproduce similar steps without any script directly from console with an already build in driver (I do not know if the library what I used is also possible to use with Pi4, but it was a part of Raspberry Pi OS). With this you can verified if the result will be same.
Maybe helpful can be also this
Raspberry Pi Raspberry Pi I2c | Raspberry Pi (electronicwings.com)
BR, Jan