Force of Will passive ignores maximum mana from weapons

Without any gear on, my max mana is 983 and my Arc has 0.95s cast speed: https://i.ibb.co/RC4hyLx/no-gear.png

I have permanent Arcane Surge and Force of Will from the Stormweaver ascendancy, so raising my mana should improve my cast speed.

Equipping only my weapons raises my max mana to 1463 but Arc's cast speed is unchanged: https://i.ibb.co/4V1f0sZ/weapons-equipped.png

Non-weapon slots such as chest seem to work properly with Force of Will: https://i.ibb.co/zsTbX6j/chest-equipped.png

None of the items have cast speed on them:
https://ibb.co/V3NJv4P
https://ibb.co/ykLmdFV
https://ibb.co/tPKpdK7

This seems to apply to the mana regeneration multiplier of Arcane Surge as well. Manually calculating my mana regeneration gives me about 5% more than what's shown in game as long as I have my weapons equipped.

Entire passive tree at time of testing in case it's relevant: https://i.ibb.co/jW3G5fW/passive1.png https://i.ibb.co/kJLHgnJ/passive2.png

After testing this ingame with spending 800k gold on un- & re-speccing, I can confirm that Force of Will apparently does not apply to weapon & offhand stats :(

Edit: even % increased mana from soul cores is being ignored on shield slot

Same issue here

Same issue