Radials, if you believe the propaganda, are a part of the suspension, bias are not.
That is the crib notes version. Some say a bias suspension can get squirrely if radial tires are used, or is it the other way around
Anyway,IIRC radials on a bias suspension is bad, the other way not as much but still not optimal.
I don't understand all the bias against bias tires, but understand they should be on the right suspension. Some say the radials last longer, handle better and stop faster, I haven't had this experience with them, but "they" say it.
XCT, XC, and I am sure the other X bikes have a radial tuned suspension. As for the Metzlers, well, you said to leave out opinions. 888's are sold in radial form and the 880's IIRC again, are sold in both.