it might be a difficult bug to solve, but the Network of Castles (and the Network of Citadels in that respect) are still apply inconsistent attack speed bonuses to the units.
Their neither provide full attack speed, nor the the same amount, nor consistently. The bonus for the Network of Castle is also listed as 20%, which is also wrong and the NoC doesn’t always apply the bonus to the units in the vicinity.
This bug isn’t tracked here. So I’m trying to provide more visibility, since I also think that this also solves a balance issue with that civ.
The bug is mentioned (among others) here:
someone from the community provided this nice table of the real vs supposed values: