Based on their description and lore (from the first game as well), Soulbound weapons should be universal and any character whose soul is bound to them should be considered proficient in their use. Hence, I would expect a Devoted not to take the -10 Accuracy penalty when wielding a Soulbound weapon, regardless of whether it is of the kind they are devoted to.
Currently, that is not the case:
Is this intended (i.e. the Devoted's restriction is meant to apply to Soulbound weapons too) or are Soulbound weapons mistakenly not flagged as universal in the current beta build?