FYI, I ran Darshan's repro on a 15.7 SP103ish bin_iso_1 2KB server using apl locking and server level histogram steps=50/tuning factor 20.
Ended up with 500 after index creation and 175 steps after update index stats
Histogram for column: "col2"
Column datatype: integer
Requested step count: 50
Actual step count: 500
Sampling Percent: 0
Tuning Factor: 20
Histogram for column: "col2"
Column datatype: integer
Requested step count: 50
Actual step count: 175
Sampling Percent: 0
Tuning Factor: 20