Yep. That's another known limitation of the PB addin with UFT. Although it's not mentioned in the Addin guide, it has been around for a while and is documented on HPE's support knowledge base site. I won't post the article here because you'll need to log into HPE's site to find it anyway, but do a quick search for UFT and PBDataWindow and you'll find the article as the first link.
What happens is that UFT identifies the PBDataWindow as a table, and all of the objects inside of that table are cells. Every edit field is a cell (like in a spreadsheet for instance) and you can navigate them by methods such as SetCell, GetCell, etc.
I think it will make sense when you read the KB on their website and you can easily work around the issue just like you would a WebTable or similar object.