After reading the whole tread carefully, my understanding is that without the users action, google has the opportunity to collect metadata every time Joplin starts. It seems to me that this is primarily an electron design decision, the amazing people here could provide a workaround, in my best case.
Dictionaries do not update frequently. I could understand if there is a connection once, when a new dictionary gets activated for the sake of convenience. On every start that really seems gross. Personally, I wouldn't mind to download the dictionaries my self and add them to Joplin.
It might be of value to create a wiki entry, with the instructions for the privacy aware user, to make sure no metadata leaks to big tech. I always was of the opinion that Joplin is completely offline, therefore I volunteer to contribute to that.