It's comparable to working in a butcher that specialises in pork. Clearly, the job would be unsuitable for a Muslim or vegan jobseeker. That's why the government website specifies suitable jobs and has an exception for a good reason not to do the job.

I agree with the general principle that not all labour is the same, but I don't think prostitution is in a class of its own. If you paid me enough I'd probably do it for a week and then retire.