Yes it does. Whiteset is not classed as a solid product because it is so soft and can be scratched with a fingernail, therefore no adhesive will stick to it properly. It’s like putting adhesive on the back of a tile, putting it in a sand pit, and hoping it stays there.
Unless we are doing the demo for you and this has been factored into the quote, we can’t start work until the whiteset has been removed. I can advise you of the best piece of hand-held equipment to do the job though!