When adding a delay to a feedback survey send, the intended recipient must continue to meet the send criteria until the delay period is over. However, the current explanatory text on the Recipients tab regarding delays seems to imply that the intended recipient will always receive the survey after meeting the required criteria, and does not make clear that the requirement that they must continue to meet those criteria for the entire delay period.
I recommend editing this text to make this requirement clear, as some recipients may otherwise go unsurveyed.