When you scroll down, you instantly go from the top to the bottom, 2 new rows appear - usually you can scroll in 1 row increments.
MC-83709
Scrolling in the "Miscellaneous" creative inventory tab skips one row
Resolved
Fixed
0
Also applies to the Combat tab. All other tabs either have far more rows, not enough rows to require/allow scrolling at all, or only 1 additional row (Materials).