I don't understand what you're saying about linking. 'Under' is an ordinary preposition when followed by a noun phrase, whether it has its literal meaning ('under the table') or is used in idioms ('under oath', 'under pressure', 'under an obligation', 'under the circumstances'). It can also of course be a prefix ('under-age', 'under-performing'), but that doesn't affect the prepositional use.
Sorry, by 'linking', I meant something like 'describing'. Anyway, thanks for the explanation. I was just confused/unsure because I didn't know if 'under' would still count as a preposition if it wasn't used in the literal sense.