I don't understand the fascination with blur. It's terrible from a security/privacy perspective. The data is still in the image. Sure you can add randomization to the blur to make it less easy to undo(I haven't looked if Flameshot does or not, most don't). If you crop the stuff you want out of the image, there is no data there to do anything with. Every screenshot tool I've ever come across has a blur tool but no cut…
With blur there can also be no data (as you said -with randomization, you can even blur randomized text instead of the real one). But the fascination is easily explained - it looks better as it "fits" the rest of your image vs having some jarring black rectangle
I've never ever seen that in the wild, but that would def. make it sane to use the blur tool.