It turns out that the tooltips had not been completely parsed correctly.
When originally doing the testing on rishu, I ran into an issue that the Test::Unit::XML gem wasn't working correctly. It would accept two radically different XML paragraphs with doctype headers and say that they were equal.
After some amount of digging, I found this bug on the REXML tracker. I made the (one-line) change provided and suddenly Test::Unit::XML started working again.
The ruby install on winry provided with a newer version of REXML than what was on rishu. However, it still did not incorporate the fix in the bug report. Unfortunately, I used winry to validate the item tooltip XML since it was faster.
After adding the fix to REXL, the validation script is dying because there are still unimplemented tags. Yay for more work.