Does this guy even have any information on possible unannounced titles? How would he know that then..?

Nintendo has already teased Pokemon, Fire Emblem, and Metroid. Plus they’ve shown off a lot of the interesting looking multi-plane Yoshi game. Add in a possible Animal Crossing to capitalize on the mobile app marketing; realistically, they should have hit that metal while it was still hot, but it’s still better off, brandwise, now than it was before. Tak also teased an XCX port.

So my prediction for new stuff announced for the rest of the year from Nintendo:

1. Yoshi - almost certain.
2. Fire Emblem - almost certain.
3. Pokemon - highly likely.
4. Metroid Prime - highly likely
5. Animal Crossing - Likely
6. Xenoblade Chronicles X - likely

Those go on top of
* Mario Tennis
* Smash Brothers sequel
* Donkey Kong Tropical Freeze
* Hyrule Warriors remake
* Toad Treasure Tracker

I don’t think any more than this from Nintendo, since that’s already a nice stack for 2018.

"when we look at the slate of titles -- many of which haven't been announced yet"

Many of which? Nintendo already has 3 of their own games slated for the second half (Fire Emblem, Yoshi, Smash) plus they probably count Octopath Traveler as the tentpole release in July. We can really only expect 1-2 more 1st party games announced/confirmed for this year. Thus he has to be refering mainly to 3rd party games then, and they aren't exactly the driving force behind Nintendo systems like they are elsewhere, but they're still very much helpful. It's already great that Nintendo is putting out games frequently n consistently, and now it's even better that the small gaps between 1st party releases will be filled with 3rd party.

I don't really think Prime 4 or Pokemon are more likely than Animal Crossing .... which is ironic given they were announced earlier, but...

I think Smash + Animal Crossing will be their big first party releases for the holidays. I really hope they're not rushing out Pokémon, I don't want another barebones game like X/Y...

I've only ever seen Nintendo announce a new AAA game once ahead of their other previously released in-house projects in this generation so far ...

WII U Announcement: Pikmin 3 (2011), SM3DW (2013), XCX (2013), DKCTF (2013), MK8 (2013), SSB (2013) and Splatoon (2014) 

WII U Release Order: Pikmin 3 (2013), SM3DW (2013), DKCTF (2014), MK8 (2014), SSB (2014), XCX (2015) and Splatoon (2015) 

Switch Announcement: Zelda (2016), Splatoon 2 (2017), SMO (2017), XC2 (2017), Pokemon (2017), MP4 (2017) and SSB (2018)

Switch Release Order: Zelda (2017), Splatoon 2 (2017), SMO (2017) and XC2 (2017) ...

Not unprecedented since it happened with XCX on the WII U and it'll eventually happen for some games on the Switch too but judging by past odds I'd give the likelihood of another AAA game being announced for the Switch this year being roughly 20% however, if Nintendo truly had another project to release this year they would've most likely announced it by now when the first half of the year is almost coming to an end ... 

I don't think that Pokemon announcement should be counted as a real announcement. They literally only said it because of the fan's rage over Ultra Sun/Moon.....and therefore, you will see it release after games that are announced after it.

With Nintendo's new strategies they announce games way closer to release than before. So lets at least wait until their E3 to give a judgement.

They officially announced an entry for the Switch during E3 2017 ...

True, you can totally count it as an announcement. Fair enough.

What I am saying is I'm 100% sure they announced it way before than they were supposed to. There was a Pokemon Direct 6 days before E3,  which announced Pokemon Ultra Sun/Ultra Moon for 3DS. Especially after all the pokemon stars rumors, a lot people were furious about the announcement. Which lead them to shoehorn the announcement of Pokemon for Switch in E3 just to assure all those people the game is still coming to Switch.

Thats why Pokemon may be out of sync in the diagram. Within that wait for Pokemon, Smash will be announced and released.

Retailers and especially GameStop are tied in with Nintendo, Sony, Microsoft, and a few other big publishers on the promotional side.  They work with them to plan out promotional material.  To that end, they often get notified well ahead of time about upcoming announcements to prep for promoting preorders and releases.  The YouTuber Spawn Wave used to work at GameStop and explained this briefly in his video discussing this.  GameStop also owns Game Informer, a gaming news magazine.  With E3 coming up, Nintendo will be in communication with GameStop concerning promotion and coverage in Game Informer.  So yeah, top brass would know.