The watch does not send/receive satellite text messages by itself, but you can pair it with a Garmin InReach device and then use that to send/receive Iridium satellite text messages using your Fenix. The inreach device has to be within 30ft or so of your watch for that to work.
That setup works great, I'm very happy with it. Can be in a remote place in the mountains, nowhere near cell signal, and get text messages from back home on my watch.
GPS is one-way satellite communication, you can receive signal from the satellites but you cannot send data to GPS satellites (with any device). The Iridium satellite network, which is different than the GPS satellite network, allows 2-way communication but it requires a large and very powerful antenna to do so. It's unlikely that any wrist-watch will ever have Iridium capability, because there just isn't room for an antenna that big, and for the battery it would require. The smallest Iridium device I know of is the InReach Mini, and would allow you to do exactly what you're wanting to do, the only downside being that you have to carry an extra device with you (but it's quite small and light, like 3-4 ounces)
