What most often happens is that in training sessions, the trainers give the sales staff information of all types about what is being sold. The trainer reviews the features of the item, how it can be used, the ostensible advantages of buying the product, etc.
The sales person absorbs all of that information and begins using it. Seldom does the sales person personally investigate and verify what is being given them in a training session, particularly as it involves areas that involve matters of technical expertise. It's unlikely that the car salesman has personally the stopping distances of vehicles in braking tests, for example. They presume, as do most of us when we are trainees in similar settings, that the information being given has been reviewed and vetted elsewhere in the organization by someone who has the ability and resources to do so.
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The point of what I'm saying is to shift the blame for statements such as this away from the sales person and to the organization. When salespeople make statements such as this it really indicts the developers sales organization, not the salesperson. (And for the moment I'm excluding sales people who continue to use a line even after they know it isn't true.)
A good sales organizations doesn't feed unsubstantiated information to their sales staff to use on the sales floor. It's also been my experience that that most sales people, even in the timeshare industry, do not intentionally lie.
Of course, as I noted above there are sales people who can and do mislead and lie with little impunity. Perhaps the timeshare business has a higher than normal ratio of such people. I can't say if that's the case. That certainly has not been my experience, but that might reflect that we've always been a bit more selective about the organizations at which we've interviewed.
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Of course, ethical sales people will tend to gravitate toward ethical sales organizations, with the converse equally applicable. The result, of course, is that the most predatory sales operations are also the sleaziest.