First of all, thank you for providing an update on the rumours you heard about shortly after the Direct Partner Showcase, the transparency is more than welcome.
Still, I also wanted to share my piece on the part of the rumblings about the Indie World, since you specified that you originally heard it was going to be aired before the GDC and then plans changed. Now, I want to immediately preface that yes, plans can indeed change and it is far from impossible for an event to be rescheduled to a different date; however, I have to admit I'm generally very doubtful of rumours stating that an event is happening in a set time frame and then an update comes about how that specific event is suddenly delayed by several weeks and then it actually doesn't happen at all. Under normal circumstances, that tells me that such an event never existed to begin with; and I prefaced by saying "normal circumstances" because I don't think there ever was any relationship between this Indie World presentation and the original rumour about the Switch 2 reveal in March, but I say this also by looking at what else happened in February and March.
Presumably, Nintendo set the release target of Switch 2 for Q1 2025 a bit before relaying the decision to their development partners, so before mid-February (maybe January? IIRC that's what Andy Robinson from VGC heard); still, in that timeframe, the plans for the Nintendo Direct Partner Showcase of February went ahead as expected. Or rather, almost as expected because they did get altered in the end but by something external to their control, Microsoft suddenly having to reply to the rumours about their next phase of their multiplatform push with a specific clarification about it. It wasn't Switch 2 that delayed the Partner Showcase by a few days, it was the Microsoft's podcast.
And neither the release dates for Paper Mario and the Thousand Year Door or for Luigi's Mansion 2 HD changed: since it's clear that the plan was always for those dates to be announced on MAR10 Day, Nintendo had even more time to look into the situation and see if they needed to reshuffle things a little bit to cover some gaps caused by Switch 2 releasing in Q1 2025, but still they didn't.
Therefore, I don't think the Switch 2 release timing counts as "special circumstances" that could kind of explain events suddenly missing specific deadlines if not downright disappearing; other events went on just fine, so why would an Indie World set in the same month as the MAR10 Day video see such radical change of plans? That's why I believe that the pre-GDC Indie World was never a thing to begin with, events don't normally change plans to such a degree of being a month off their original dates or downright vanishing; probably the same fate happened to the part of your rumblings about the April Direct as well.
I want to conclude by saying that this isn't me calling you a fraud because you demonstrated in the recent past to be reliable enough with your rumours, you are not part of the group of self-styled rumour mongers who just whisper to people's ears what they want to hear or clout-chasers who use other sources' rumours to try and claim small pieces of Internet fame. After all, you broke the news about the Switch 2 releasing in early 2025 and you knew about the original date of the Partner Showcase of this February after all, it wasn't your fault. However, I definitely wonder about the sources that relayed to you about the March Indie World and the April Direct, to the point where I wanted to ask you (obviously, reply as much as you're able to) how connected these specific sources you heard from typically are and how reliable they've tended to be the other times you're gotten in contact with them. Again, it's just that I usually interpret hearing about events vanishing like this in thin air as a strong sign of very incorrect information coming from somewhere in the chain.