Well, if he's right about the traditional February Direct being a partner direct, this makes sense. Nintendo as a publisher have managed to maintain a steady output of games over the past 7 years. And it is highly speculated if not known that they have sat on games for a while before release as well. So for the release schedule to suddenly dry up (only Luigi and Paper Mario planned for the April-Sept timeframe) suggests either things came crashing down or the new console is coming sooner than one might think.
While September seems like the earliest it could conceivably arrive, I don't think Nintendo needs a huge window between announcement and release. The initial announcement of NX came early because the WiiU was such a failure; that obviously is no longer needed. But the October 2016 reveal trailer needed to be early to get people to adjust to the concept of the Switch. If the form is largely the same, do we need that time for the Switch 2? And the Jan 2017 presentation, which was the blowout that revealed key details including the price, came less than 2 months before release. So while I highly doubt it is the case, the system could still conceivably arrive in June.
If not March for announcement, it has to come soon. No way is Nintendo HAS to take the Switch 2 into account for their next fiscal forecast. Also, as an aside, IF the Switch 2 is as powerful as some hope and (combined with the fact that games tend to be more scalable these days) therefore that more third party parity is expected for the Switch 2, it would be in Nintendo's best interest to allow 3rd parties to start marketing Switch 2 versions sooner rather than later, and therefore in their interest to end the secrecy before Summer Game Fest. Is Square making a Switch 2 version of Visions of Mana? Is Capcom bringing Monster Hunter Wilds over? Who knows? But every day that goes by without an announcement of it is another day where potential customers are lost.