Zappa: So you are in essence S----------D !
Maybe not.
the two essential components of the employment relationship are the provision for work or assistance in exchange for remuneration. "Remuneration" can be in money "... or in kind".
The key might be in "renumeration".
What does it cost the WTS to house and provide for each Bethel worker each month? This is a taxable amount that a person has to pay personal income tax on. At least, in Canada you do, if you are employed in a 'regular' job. For example, if a person is provided with a meal by their employer (like on a film set or something...) they have to pay personal income tax on the amount the meal is worth. The meal is included in their gross earnings.
The WTS is treading in the murky water between 'volunteer' and 'employee'. Giving a 'volunteer' for a charitable orgainzation a bit of spending money is reasonable. But, the premise of that is to provide for someone who is probably part of a larger community and working at another job or someone who may be retired and helping out. For incidental purchases that they might have. Like an honorarium, sort of.
But, with Bethel, it is different. The WTS is giving the workers much more than that. Shelter. That is compensation that benefits the Bethel worker and is therefore considered "income". They received compensation "in kind". Which, somehow, blurs the line between "employee" and "volunteer".
I think it would be worthwhile pursuing this further with a lawyer. Different lawyers will also have various viewpoints and jurisdictions. What may apply in one country may not in another.