Do you suppose the standard by which those unfortunate "random quality control RQ" folks are checked is a lot less stringent than that for targeted RQs?
The actual approach taken in assessing RQ'd applicants is deep behind the curtains, and perhaps varies from one local office to another local office, from one processing agent to another processing agent, from one citizenship officer to another citizenship officer.
And there is probably a spectrum of scrutiny depending on many factors, including overall impressions, especially as to an applicant's credibility . . . meaning that the degree or severity of scrutiny employed in a particular applicant's case can be (probably is) influenced by factors specific to the individual.
The legal standard is the same for all applicants: the applicant has the burden of providing proof beyond a balance of probabilities, which is comparable to the preponderance of the evidence standard which is common in many contexts in U.S. law.
Thus, my guess is that in the abstract, most RQ submissions are approached relatively equally and not particularly stringently UNLESS or until something about the submission, including omissions, triggers more elevated scrutiny . . . that is, that the practical standard of scrutiny in a particular case is probably telescoping, the intensity of scrutiny related to whether the information provided readily completes a picture which makes sense or, in contrast, invites questions or suggests gaps. This would not depend much on whether the reason for being issued RQ was QC or a specific risk indicator.
That said, other than the random QC RQ, these days it appears RQs are not lightly issued, that if RQ is issued there is a significant concern, and of course any significant concern is going to invite elevated scrutiny. So in that sense, in the practical sense, the more-or-less for-cause RQ is (probably, my guess) likely to face more intensive scrutiny than a randomly issued QC check RQ.
Some other observations:
Remember that reporting here tends to be imprecise. I am wondering whether the random Quality Control instances involve what is sometimes called RQ-lite, the CIT 0520 form, in contrast to the full-blown RQ, which is CIT 0171. The CIT 0520 makes more sense for Quality Control.
It is interesting that the forum has seen at least three or four recently reported instances of RQ for QC when, in contrast, this had been rarely reported for quite a long while.
If those who say they have gotten RQ could specifically and correctly report which specific form they received, that should help, at least somewhat, put some of the information into context. In particular, it would be helpful if those who receive RQ could indicate the form number, including the date -- most recent version of the CIT 0520 form I have is quite old, for example, as it is CIT 0520 (10-2013) E, meaning it is the English version issued in October 2013, and the most recent version of the full blown RQ form, CIT 0171 I have a copy of is the CIT 0171 (07-2014) E version, so it is not the version in use for any application made after June 11, 2015. (And of course they will necessarily be a whole new version necessary for applications made after October 11, 2017.)