is the reason pokemon sword and shield are doing so poorly because people are waiting to know more about each game to pick which version to buy?
Their release is still a full pregnancy period away, they are actually charting not too badly by that metric. What's more, PLG certainly steals some of those early preorders right now since it is, well, already available right now and not just in 9 months.
There are certainly also small groups who can't yet decide, wait for a double pack or a special Switch bundle. But I think the above is much more true right now.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/