Qt by default uses native widgets wherever possible
Not true. Qt widgets appear to be native, but in fact they are not (but your post is proof that they made quite a good job with the appearance). This is a bit of problem on macos where Qt has some issues with appearance (or at least used to have).
And over there, I'm demonlapin (925).
Adding manpower to a late software project makes it later. -- F. Brooks, "The Mythical Man-Month"