Bonus damage added before crit multiplier?

Disclosure: This may be working as intended, I am simply sharing math to the community for their opinions and to see if this is ideal.

TLDR: Due to the base damage directly being increased rather than getting bonus damage as flat damage, assassins crit bonus amplifies the effects of items thus increasing the value of the item itself.

I am not a math expert but watching Akali's damage with the assassin 6 buff had me wondering. Why is Akali doing so much damage when her base damage is so low. So I looked at the math and these are the number I came up with:

How I thought it worked: Typically most damage in league is additive not multiplicative. Meaning if you have two items giving you bonuses for example 20% attack speed. You did not directly get 40% attack speed, instead your base attack speed would be multipled by the bonus 20%(1.2) and then it would be done again for the second item and those two numbers would be added together to get the final amount.

Math example: Using tft Akali; At 1 star, Akali has 200 base damage on her ult. Lets put a death cap on her. She now gets 50% increased damage to her ult. It now does 300 damage. If damage is additive then a crit would be bonus damage and not count bonus damage from another item instead adding it to the math. So she would have 200 base damage and 100 bonus damage. The crit would multiply the base damage then add the bonus damage. In this example the math would be 200 * 3.5(350% crit) + 100 = 800 damage.

How it works: Bonus damage is applied before the crit multiplier. Meaning the 50% increased damage is added directly into the base damage, as if the base damage itself was higher. Meaning the math is instead 300 * 3.5 which comes out to 1050 damage.

Edit: moved TLDR to top from bottom.