those two set screws used to pin it to the receiver is a weak link, hard to ensure the barrel is square to the boltface, nothing beats a threaded barrel when it comes to precision
It is curious, then, why AnschĂĽtz does not thread their barrels to the receiver? Just visualizing the assembly process and mating of parts, I cannot see how the set screws would cause misalignment of the barrel, they drive the barrel shank into the receiver until the barrel shoulder butts up to the receiver face. All squareness of the final assembly is the sum of the squareness of the receiver face to barrel shoulder mating, and having the barrel shoulder cut true to the barrel shank, breech face, and bore. Then the receiver machining, bolt body machining and bolt lug machining must also be dialed in to the breech face.
I cannot imagine CZ dialing in each and every single component for each and every single rifle, like, come on... it's CZ

AnschĂĽtz rifles aren't even dialed in to that extreme level of precision, so the 452's certainly aren't either. Anecdotally, despite the 452 having two bolt lugs, contact is usually not even and often only one lug makes solid contact (ask RFC gunsmith djdilliodon, who is my source on this). Anecdotally as well, barrel shank, barrel shoulder and receiver faces of AnschĂĽtz rifles are not precisely true as well. I base this on buying a replacement 1416 D HB barrel and dry fitting it into two AnschĂĽtz receivers, a Weatherby XXII and 64 MSR. In the XXII receiver, the barrel shoulder made contact only on a thin strip of the receiver at 12 0'clock, and in the MSR receiver only at 9 o'clock. I can show you pictures where I applied dry erase marker to the parts and contact is shown where it wore off. It is plausible that the originally fitted barrel to an AnschĂĽtz receiver is dialed in for a square and full mating, but I did not have a way to test this at the time. When you understand how metal shifts and moves on a day to day basis, it is no surprise that two components manufactured on different days have a low chance of being dialed in to each other, they need to be fitted on the same day to each other.
We need to remember that rimfires are a different animal than centerfire, what applies with the big bore doesn't always neatly translate over to the smallbore. If the boltface squareness to the barrel has any impact on rimfire accuracy, it is most certainly very minor, and probably lost in the noise of inaccuracy due to inconsistent ammunition and an out of tune barrel.
455's ain't accurate, eh? What say ye to this? (Not my target)
http://www.rimfirecentral.com/forums/showthread.php?t=921017&page=4 I would hardly say that the set screws are holding back accuracy in the 455 to a significant degree. What seems to be the most important factor, trumping all else (assuming other aspects of setup aren't defective/deficient) is a quality barrel with a match chamber. That's where your accuracy comes from. My theory is that CZ has lowered their production standards in recent years, I would need to get my hands on some 452's to inspect and analyze to confirm my suspicions. Early implementation of the 455 naturally had some bugs to work out, and with the C series that I've seen lately, they're nearly there, but for the consistency of barrel quality.