It's tricky to guess the 9 third party games included in this tally; Monster Hunter Generations is confirmed, Crash Bandicoot, Minecraft, and Diablo 3 are basically a given, though beyond that its hard to say. Maybe FIFA 19?
I haven't been paying attention to the Switch eshop charts, were there any digital games that were super popular? (Excluding free to play)
Monster Hunter Generations Ultimate barely makes it because more than 200k units of its total were sold in Japan where the game released in August 2017, so in a different fiscal year. Still, the 1.2m figure you posted earlier was by the end of December 2018, so the remaining quarter most likely pushed the game over the edge.
Octopath Traveler is 100% sure because it has already been posted by myself. Crash Bandicoot, Minecraft, Diablo 3 and Mario + Rabbids (continued good sales because of frequent discounts) bring the total to six, leaving three other games.
The list of the top 10 third party games in the USA helps here:
Just Dance 2019 should make the cut because the IP continues to enjoy modest popularity each and every year in both America and Europe. LEGO The Incredibles is a good candidate because it released in June 2018. The other games on the list have either been already covered above or were released during the fiscal year before the one this topic is about.
Rocket League has been a steady seller and it has a physical version which is mandatory to be eligible for Nintendo's statement. It not showing up on NPD's revenue-based ranking isn't surprising because the game has a low price tag (same reason why Minecraft is not on it).
FIFA 19 is possible, but if I remember correctly, it had an abysmal LTD of less than 30k by April 2019 in the football-crazy country of Spain, so that doesn't bode well for European sales as a whole. I'd rather go with Just Dance, LEGO and Rocket League for the remaining three third party million sellers.