I've been shooting a CZ 457 MTR in ARA factory bench rest for the past year and have been doing pretty well.
Just a guess on my part, but I think the MTR is overwhelmingly the preferred CZ for this type of shooting, so CZ did something right.
But just like any other rifle, particularly a factory rifle, you pay your money and take your chances when it comes to accuracy.
I purchased another factory barrel at a decent price just to see if there was an improvement in accuracy and found they were about the same, so I put that barrel on a CZ 455. Now, that was an improvement over the 455 factory barrel.
I'm shooting Eley Tenex in mine because with the current ammo shortage, I can still buy bricks of it with the same lot number. If I could do the same with Lapua, I'd try it. It did take about 500 rounds through it before the barrel showed it's accuracy potential, but it shot pretty well right out of the box.
I don't pay that much attention to what I read off the internet. You don't know how good of a shooter the posters are, nor the conditions they are shooting in. By shooting the rifle in bench rest, I've learned it doesn't take much wind at all to open groups. Shooting off of a front and rear rest will show you how the rifle wants to be held. Wind flags are your friend. I look for a dead calm day to try out a new lot of ammo. I look for a day where there's wind to practice my target shooting.