Except that the one in the demo wasn't, enabling the hack: It was discovered that the receiver that Fleming had been using was not, in the phrasing of the time

Except that the one in the demo wasn't, enabling the hack: It was discovered that the receiver that Fleming had been using was not, in the phrasing of the time, syntonic. It wasn’t tuned to a specific frequency, excluding all others, because a syntonic receiver would have been too large to use in the demo.