Sometimes when a reviewer rejects an edit as too trivial, what they mean is that the benefit it would provide is too trivial to really know that it definitively improves the post.
Sometimes an edit is quite small, but is easily improved, because it clearly make the post better. For example, if I see an edit that adds missing spaces after a few periods that end sentences but not paragraphs (
Like this.Periods, but no spaces.Pretty hard to read.), I'll approve that edit.
On the other hand, if I see an edit that totally rewords a big long post, and it doesn't seem like that wording is better than the original, I may reject it as too trivial. (I will more likely use a custom reason, to explain precisely why I am rejecting the edit. It depends if I think the canned rejection reason will make sense.)
In this case, a highly incomplete list of games serves to show that there really are games, some of them new, and many of them quite popular and graphics-intensive, that run well in Ubuntu with Wine. I consider that to be quite valuable, but if I'd been reviewing your suggested edit, I would probably have reject it as well, since it doesn't clearly improve the post it was editing. I'm not always the most efficient user of words myself, but sometimes brevity itself is to be valued in a post.
Still, I'm glad you posted that list in a separate answer. If I'd been reviewing your edit, I would probably have rejected it with a custom reason suggesting to post it in a new answer.
So to answer your question ("[W]as it really trivial?"): It depends what you mean by trivial. In this case, it's unlikely the reviewer intended to say that the work you'd put in it, or the volume taken up by the new text, was small. Instead, they probably didn't have a high enough degree of belief that the edit would improve the post, to feel comfortable approving it, especially since if it were approved, it would have taken up most of the post (visually, and by number of words).
Even rejected edits are saved in the system (they're in your suggested edits history), so even if you lose the text yourself, you can retrieve it and use it to create new posts or for other purposes.