Exporting a file does not give you the original, it changes the date which is probably the most important detail when searching at directory level,
Factual error no. 1. The date of the Photo does not change. The date on the file might, but that's of no relevance. Take a second to learn the difference betwwen file data and photo data. (1)
We should be able to store them and locate them as we choose
Factual error No. 2: Read the thread. You can. Anyway you choose. Different decisions have different consequences, of course, but you can store your files any way you want.
(1) Remember a File is just a container. That Word file is not a novel. It's a box with your novel inside it. That Jpeg is not your Photo. It's not even an image format. It's a compression format designed for holding images. Your photo is inside it.
There are two kinds of metadata involved when you consider jpeg or other image file. One is the file data. This is what the Finder shows. This tells you nothing about the contents of the file, just the File itself. The problem with File metadata is that it can easily change as the file is moved from place to place or exported, e-mailed, uploaded etc. Photographs have also got both Exif and IPTC metadata. The date and time that your camera snapped the Photograph is recorded in the Exif metadata. Regardless if what the file date says, this is the actual time recorded by the camera. Photo applications like iPhoto, Aperture, Lightroom, Picasa, Photoshop etc get their date and time from the Exif metadata.
When you export from iPhoto to the Finder new file is created containing your Photo (and its Exif). The File date is - quite accurately - reported as the date of Export. However, the Photo Date doesn't change. The problem is that the Finder doesn't work with Exif.
So, your photo has the correct date, and so does the file, but they are different things. To sort on the Photo date you'll need to use a photo app.