How is Covert Ops speed calculated?

There are several bonuses to covert ops speed:

• Playing as ARC gives 30% / 40% / 50%
• Soul Discerner Training reward from artifacts gives 25%
• Political trait Subtle gives 15% / 20% / 25%

Considering that energy and science steal is 20 turns each with no bonuses.

[edit] Actually, Energy steal is 25 turns without bonuses, so that explains the difference.

Then, (assuming it's not cumulative because that would make 0 turns for all ops) it should be

• 20 * (1-0.5) * (1-0.25) * (1-0.25) = 5.6 (might be rounded to 5) with Subtle trait at 25%
• 20 * (1-0.5) * (1-0.25) * (1-0.15) = 6.3 (No way this is rounded to 5) with Subtle trait at 15%

Yet, with ARC bonus at 50%, the 25% from Soul Discerner Training and the Subtle trait at any level, it takes 5 turns for energy steal and 4 for science.

First I would expect to have the same value for both ops, then, why is the Subtle trait level not making any difference?

Is there a hard cap here? If not, how is this calculated?

(All these values are taken for agent levels of Agent and Special Agent and are the same for both)