guz I think thats the case with any LSP if you mix and match manufacturers...OPT are just saying it loud because they can not guarantee durability if you use other polishes which may or may not contain fillers. OPT is certain their polishes do not contain fillers thats why whey recommend to stick within the manufacturer line. I always suggest that too...for instance some people polish with Menzerna but use Gyeon prep afterwards. Who is to say that all the polish has been removed. You cant be 100% sure!!!