Your histogram as you see in the converters and editors is an output histogram. It’s showing the pixel values as being send to the output device. That’s what I’m concerned of. An input histogram is based on the digital values of the raw file. They still have to be processed to a RGB pixel value with which we work. Do you think you’ll see a difference between a channel value of 254 and 255?? And what exposure setting difference during shooting will result in that numerical difference?
I’m coming a bit late, sorry, and I did’nt read all the thread. But I’ve been shooting RAW with Canon for several years and I’ve used DPP at the beginning. I’ve downloaded your picture and opened it in DPP: your Picture Style is “Fine Details” which is the best imho when you want to see the best sharpness you can get on the back LCD of your camera. When you open it in DPP, the JPG you see is already sharpened, which is not the case with the minimum processing you have chosen in PL. The difference is there.
I hope you don’t mind, I did my usual processing on your image. My crop isn’t as tight as yours - I personally think your crop is too tight and smothering the bird. Sometimes, less is more (it’s an old UNIX saying).
Your image has a Blue cast on it and I have done my best to mitigate that Blue cast.
I used Lightroom Classic and Photoshop, only doing some very minor sharpening in Photoshop. I can happily share my edited .tif file with all the layers if you want. There was quite a bit of masking in both applications btw.