No remaining security funds must be new, last time I was able to see remaining funds was early January and I have not flown any trips like that afterwards. If there are no remaining funds then you'd not be able to 'finish' the trip and have funds post. Best is to only use points for hdden-city trips.

WN is really making hidden-city trips harder even without explicitly prohibiting them. One of my recent trips AA-BB had a continuation to CC (a cheaper destination than BB) using the same flight number, but it was not an option to book it as a direct flight (AA-BB-CC). I've also seen connections in BB disappear with only AA-CC shown on the website.