not every enhancement is a buff. barriers, auras and selfstacking buffs are not removed by han.

there are more or less two kinds.

the first is the kind that says: 'every time this unit do something stat X will be increased'.

examples are ninjas like roshi, kimimaro, edo deidara, kushina habanero or main passives like nature energy gathering for azure fang.

the second is the kind that says: 'increases stat Y for each Z thing that happens'.

examples are ninjas like ay 3rd, chojuro, hinata dreamworld or main passives like queen momentum for breeze dancer.