Possibly, yeah. The trouble is we don't know what criteria puts people on the watch list, because (as with all these debates) we don't know (and can't know) how the intelligence services operate.
It could be that you only end up on the watch list after very intensive research - in which case, fine. It could also be that everyone who's even the slightest risk gets put on the watch list in hopes of casting a wider net, or even that some non-risk people are put on it on the assumption that some enemies are able to read it, while only those in the know understand which ones are the real threats etc etc.
These are the kind of mind games you get into very quickly with intelligence work, and the watch list hasn't been designed as a go-to list for detainment. It could also be that the various agencies are in the process of building cases against people for the purposes of a trial, which takes time. We don't know - and, obviously, we can't know because then our intelligence services would be completely exposed.
This is ultimately why these debates about what should be done won't and can't go anywhere. We don't have access to the relevant information about what is being done at the moment - and if we ever do, it won't be for decades. Frustrating but... well, there's not really much we can do.