This trait reads "+3 Attack vs higher level units". However, regardless of level and enemy level, this bonus is always given.
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Attack_Boost</StrVal>
<StrVal2>UnitStat_Level</StrVal2>
<Value>3</Value>
<vsHigher>1</vsHigher>
</GameModifier>
vsHigher seems broken.