Headset for Trek E-Caliber 9.6

[Wagonrd]

I replaced the Rock Shox Gold fork on my e-caliber with a Rock Shox SID and ordered a 1 1/8-1.5 headset. To my surprise the upper bearing outer diameter was 1.45mm to large for the cup on the bike. I ground it down to fit. My question is: “Why did Trek deviate from the standard size”? I analyzed that the knock block requires a bearing that flush with the bike frame; the bearing that I ground down protrudes up above the frame and prevents the knock block from engaging. I also discovered that the Trek upper bearing is not available anywhere on line. The other problem with using the original Trek upper bearing on my Rock Shox SID was that tightening the Star Nut bolt resulted in partially seized fork bearings,making the bike steering difficult. My ground down bearing does not seize up the fork when I tighten the star nut.