This is not true. The accommodation is only possible if it doesn't present undue hardship, safety concerns, etc. Plenty of accommodations can be denied on those grounds.
You could answer that yourself. To qualify this first ask what are the criteria for a person to establish a valid religious exemption request and then what are the criteria for a regulating body or employer to deny the exemption according to that criteria.
Also, some institutions have much wider latitude to deny a variety of religious exemption requests than other due to environmental hazards and safety concerns.