This seems to be running similar to the hunting ethics thread near the top. I have been fortunate to hunt upland birds in FL, TX, CO, ND, NV, CA. Some were farm or planted, most were wild. IMO, it is considered not only bad form to ground sluice a bird, it is also a safety issue, especially with dogs. We always worked on the "blue sky" rule for wingshooting- no shots taken unless you can see sky to keep from shooting someone or the dog. As to the pheasant in a tree, perhaps you could have moved around the tree to get a shot when he flew, perhaps not - that is a shot you have to determine in your mind.
IMO, there is a difference between something that is legal versus ethical or "sporting". I hunt for the enjoyment of it - if my day afield resulted in an empty bag at the end of the day, I know two things - it was still a successful day, and I can stop at the store on the way home if need be so I won't starve. I have hunted Gambel's and California quail, bobwhite, blue and ruffed grouse, chukar, pheasant among others. With or without a good dog, birds will fly eventually - but the dog does make it easier.
As to the failed analogous comparison to shooting deer on the run - not if you want to eat the meat you won't - mulies and pronghorn taste nasty if they were running as you shot them - birds, not really an issue.