Many of those telco plans in Switzerland that just add a data eSIM don’t actually work with something like an Apple Watch, which is why I assume the GP asked at

Many of those telco plans in Switzerland that just add a data eSIM don’t actually work with something like an Apple Watch, which is why I assume the GP asked at the store. At least the Apple Watch requires a mobile network to offer a special shared-number add-on and support Apple’s GUI for provisioning this plan with an eSIM on the watch. Unfortunately, this usually means sticking with more expensive first-party networks rather than MVNOs and paying whatever fees they require. It’s quite possible the Samsung watches don’t rely on this system, but I’m not sure and may have also assumed it was worth asking like the GP.