Steps to reproduce:
1) In any report create a Subreport. (An empty one is fine.)
2) Then open the Subreport's properties.
3) Hover over 'Parameters Map Expression', 'Connection Expression', et.al.
See screenshot of yellow "help".
I would expect what it says in the yellow box not to just repeat what the field title is. It would be very helpful if it gave a few examples of how to use the field.
(Some people might think that a bug in the help is not that big a deal. But if it impares significant important functionality, even if only because people can't figure it out, then perhaps it's a big deal.
When I look at the form there are lots of people who tried to get subforms working and from the looks of it never got them working. It's probably because they couldn't figure out how to get it working I think. I for one am still baffled about these various fields and I've used many subforms in MS Access.
The good thing is that these type of bugs are really easy to fix.