Whilst not impossible, Leeneia, with Niles's reputation and other odd doctored ballads, do you really think this likely?

There are several logical stages in the build up to suspicion.

Firstly the collector/poet/antiquarian presents as traditional a number of unusual and markedly different versions, or comes up with a version of a very rare ballad not seen in oral tradition for several centuries. (Plenty of examples.) Or indeed sometimes completely new ballads in the idiom.

Then the truth seekers start to examine these versions minutely and point out any anomalies, such as one person's versions being more than half as long again as anyone else's.

Then when these have been minutely examined there start to appear idiosyncracies peculiar to that collector.

The massive problem for Professor Child and indeed for any ballad researcher is identifying what is authentic and what is bogus.

From a singer's point of view of course all of this is irrelevant.