I haven't looked into any claims or followed these links, so I don't know what the limitation is.

But abstractly, it's absolutely possible to write a program that decodes frame at a time and displays them slowly.

Now, whether there is some architectural difficulty based on design decisions within their player, or any player, I don't know.

Edit: I guess downvoters have never worked with a video decoder api before? I just read the link and it seems like the rationale is to not seek one frame backwards because you'd have to seek to a key frame and waste some work? That's not the same as it not being possible.