Question about Galaxus Mobile Basic plan

Good day. I have a question about the Apple Watch. I bought my son an Apple Watch Cellular, now I wanted to ask if everything will also work on the watch, e.g. phone calls, text messages and internet, if I buy the Basic plan? I read that the phone provider has to have multisim for an Apple Watch, and Galaxus Mobile does, from what I read. I'm asking all this because I came across a website where it says that Galaxus Mobile won't unlock calls made with a watch without an iphone nearby, is this true? You can read about it here: Can I also make calls with Mutisim: https://www.moneyland.ch/de/multi-sim-karte-schweiz-ratgeber Otherwise I would take out this plan straight away if everything works on the phone on the watch etc? I hope someone can help me, thanks Lg