I keep smart notification off for the majority of time.
Sometimes I turn it on because I wait something important.
There are 3 categories: calls / SMS / apps. First is always active on my watch, I don't use SMS, so I turn on the latter and notification didn't arrive on my watch.
After many tests I found that the reason is tha Garmin Connet puts under "SMS" a lot of application, why?
Then I try to change my phone language and in English the category is called "texts", maybe in Italian could be "messaggi" so the user can guess that it includes more than one single app.