The sleeping babies are adorable.
The babies sleeping are adorable.
To me, the two sentences are identical in meaning. However, this doesn’t seem to be the case in the following sentence:
The singing sensation is a teen heart throb.
The sensation singing is a teen heart throb.
To me, the subject of the first sentence is a singer whereas the subject of the second sentence is in the process of singing.
Is there a rule for when using a present participle as an adjective does not carry the same meaning as doing a whiz deletion?
I think your difficulty lies with the fact that singing sensation is a commonly used compound term, and therefore turning the phrase around has a different meaning. I couldn’t find an online definition of “singing sensation”, however a quick search will find many examples of its usage:
Singing sensation Susan Boyle has been awarded an honorary doctorate
from a Scottish university.
There is even a website singingsensation
Sleeping babies is not a compound term, it is merely an adjective with a noun, and babies sleeping is, as you say, a whiz-deletion.
If you avoid sensation and substitute a different noun it becomes interchangeable the same as the babies example:
The singing man is a teen heart throb.
The man singing is a teen