Yes, but if HMRC do get you in their sights you tend to stay there for quite a while. Once the problem was identified PRL just seem to have failed to get a grip on it.
The overspend was £1.1m in 16/17. That's not marginal and should have been enough for PRL to have totally been on their case for more than 5 minutes. Overspend reduced to £98K in 17/18 but an overspend nonetheless, back up to £908K in 18/19 and we know they'll be over again this season.
If PRL weren't properly resourced to police their own rules that's no-one's fault but their own. Whether cock up or conspiracy on Sarries part there were red flags everywhere and if they didn't have the resources themselves PRL could have bought in auditors. You target risk and while the fault is squarely with Sarries, PRL should never have let it come to this.
IMO it's just a matter of how deep an investigation is wanted as a matter of course. It's not like the cap manager saw that sarries were £1.1M over the cap and decided not to investigate - they were lying and cheating, and gave him figures that showed that they were within the cap.
We do know that it took 8 months to go from PRL being interested (April 2019) to the investigation reporting back (November 2019) - and that's with a better funded, better manned, independent investigation being set up, with asistance from journalists and other premiership clubs (Quins having been name checked as "amongst others").
The salary cap manager is there to give advice to any clever ideas clubs have (Sarries specifically and deliberately chose to spend £3M on independent legal advice in order to avoid letting the SCM have his say); and to tidy up and apply sanctions for administrative error type overspends (extra win bonuses, loan player arriving a week early, player B not missing an England match). He's there to launch an investigation when he has evidence, not to do so in the hopes of finding evidence.
Now you or I may think that he SHOULD be there to do more, especially for a club already found in breach. But as it stands, he isn't.
I don't blame HMRC for looking at everyone's tax returns and saying "that looks about right" rather than launching an 8 month investigation into everybody. I don't blame the salary cap manager likewise.
If PRL want the SCM to be more pro-active, and to launch deeper investigations into previous examples of cheating; then that's fine - they'll need to resource it properly though - which would require, for example, Saracens' agreement. People throughout this have this habit of forgetting that PRL is the clubs. PRL needed to be unanimous to release the report; which meant they needed Saracens agreement, and without it, PRL weren't unanimous - but it got reported as "neither Saracens nor PRL want to release the report - they're both trying to cover things up"