I read higherpurpose's concern as being about the use of secret surveillance information for targeting vehicles for searches. My understanding was that they saw that as, at least, a subversion of the way a just system ought to work.

It looks like higherpurpose is over-reading "pretext" to be a false statement, but I think I agree with the sentiment that I don't really want police focusing their attention based on information that they later obscure (I would not be surprised if there are exceptions to this that I would agree with).

So the question I was formulating was about the incentive this creates for the officers (to pull people of interest over for whatever the hell) and the differing ability of those people to challenge the stop. I guess on further thought that isn't a particularly interesting question (driving is easy enough to nitpick and find a legitimate pretext that will withstand scrutiny).

Anyway, when I said 'legal theory', I meant that you were explaining the particulars of that decision more than you were addressing the concerns about targeting, and when I said 'practical outcome', I was thinking about how it would influence behavior of law enforcement more than how it would play out in court.