Not sure if this is a bug or works as intended:

Attack rolls when attacking with the off hand do not add str/dex modifier to the attack roll.

However, str/dex are added to the damage roll, even without the two-weapon fighting style.

This is the reverse of is in the PHB, was this intentional or not?

Also makes two-weapon fighting style useless?

IMHO I would be ok with this, since that can mitigate the off-hand attacks characters can make, even when using an action to cast spells