Works but is kinda useless. There is a limit to how many photos you can delete a day. I want to delete thousands of photos, I don't want to wait multiple days to do so. I'd rather just do it manually. Here's a better method, takes like 10mins:

So, I made sure to max zoom out on my library page (ctrl + "-", or alternatively use ctrl + scroll, forget which direction but it should be quickly apparent), then I was able to much more easily select hundreds of photos at a time. You MUST let the thumbnails load though. Do the whole, "select the first file, then shift + select the last file" for as many as you can load. Have yet to find a limit. Don't think there is as long as they load. I've done 3-5,000 at a time.