I cannot find a specific term for this condition. With the correct use of
hyphens, I believe the condition should never exist. As you're no doubt
aware, it comes about by the middle word feasibly being both adjective and
noun. In actual fact, for each case, it can only be one. Here is another
example:
old shark bait
If I mean bait for old sharks it should be "old-shark bait".
If mean shark bait which is old, then it is written correctly. I could also
write "old, shark bait" to avoid ambiguity.
In your example, a hot cup (for tea) would be 'hot tea cup'. You may even
see "hot tea-cup".
A cup for hot tea would be 'hot-tea cup'.
Sorry I haven't answered your question directly. It's a an interesting point
you raise.