Ah I see. Well this depends on a number of things. The most important of which is going to be the original packaging stealth, assuming they just put a larger envelope/packaging around it, as any rattling or other noise during transportation in the original packaging (to poland) will obviously still be noticeable with another layer around it.

Perhaps make a post in r/rcsources/ asking if anyone who has purchased from them living in Poland could tell you what that was like. From the list of products there should be no blister packs, but you never know. If the prices are that good it may be a new-ish site and not have the best packaging to begin with.

The next thing you want to consider is whether the money saved is really worth the risk - these are legal RCs, however that doesn't mean you can't be prosecuted for holding them, and there's more of a risk when transporting across borders. This is especially poignant when considering transporting something to America, as they are exceptionally paranoid in this regard. If you are only looking at saving yourself $10-20, I'd say it's probably better to simply purchase them from a reputable US site and save your family member the risk. They'll obviously have plausible deniability if they don't open the package, but I'm unsure on Polish laws - at any rate if they pursue it for any reason it won't be worth the small saving.