I'm afraid this might be a bug in your test case.
The process in the test case appears to be:
1. set b to all elements
2. set p to only elements in .playground
3. set bnp to be elements that are in b and removing those in the playground
4. set hover functions
5. add meta tag (note this will NOT be in bnp)
6. on hover, set s to all elements
7. set t to s removing bnp (that doesn't include the new meta)
8. t now includes everything in the playground plus the new meta
I believe if you move that meta creation to before the creation of b, p, and bnp then it will work as you expect.
Skpye must be adding the meta tag at some point after jQuery is ready (perhaps window.onload?).
So as near as I can tell at this point, this is not a jQuery bug.