Can explain %attack mutiplicative and %total/boss damage additive?

General Formula
weapon multiplier * (4 * primary stats + secondary stats) * (Weapon Attack / 100)

With % attack and boss/total damage
[weapon multiplier * (4 * primary stats + secondary stats) * (Weapon Attack * (1+%attack) / 100)] * [1+(%boss damage + %total damage)]



ex:
weapon multiplier = 1.2
primary stats = 300
secondary stats = 4
Weapon Attack = 200
%Attack = 100% = 1
%Boss damage = 50% = 0.5
%Total damage = 50% = 0.5


By the commutative law, the order of multiplication/division doesn't matter
(Weapon Attack * (1 + %attack) / 100) = Weapon Attack / 100 * (%attack)

weapon multiplier * (4 * primary stats + secondary stats) * (Weapon Attack / 100)=
base damage =
1.2*(4*300+4)*(200/100) = 2890

base damage * (1+%attack)=
2890 * (1+1) = 5780

base damage * (1+%attack) * (1+%boss damage)=
2890 * (1+1) * (1+0.5) = 8670

base damage * (1+%attack) * (1 + %boss damage + %total damage)=
2890 * (1+1) * (1+0.5+0.5) = 11560