Nintendo having a light second half of the year isn't a contentious idea per se; knowing what their dev cycles look like, if you know a big new EPD8 game isn't quite ready yet or is being saved for new hardware, there just aren't any internal teams that could reasonably have a blockbuster release lined up.
EPD3 will have just dropped TotK, EPD4 just wrapped up Switch Sports and seems to be grappling with stinky horse, EPD5 is still working on Splatoon 3 updates, EPD9 is working on the BCP, EPD10 is on Pikmin 4 (not a blockbuster). Monolith Soft is doing Xenoblade 3's expansion and the action game is presumably a ways away, Retro will put out Prime 4 some time in 2024 if we're lucky, Next Level Games just put out Mario Strikers, HAL is putting out RtDLDX in spring, Game Freak is doing SV DLC, Int Sys just put out FE Engage. Maybe Nd Cube or Grezzo has something big, or someone else is gearing up a big exclusive, but neither strikes me as likely.
I don't think it's controversial to say that they're probably right about Nintendo's post-Zelda year being relatively quiet. Most of the rumored stuff floating around is Grand and Illustrious Old Shit. The hogs on this forum will devour the slop, but it ain't gonna make waves.
The part that doesn't pass the sniff test is that Nintendo would skip E3 because of this and would inform E3 organizers that this is the case. Even if Nintendo is skipping E3, why tell anyone that it's because your release schedule is weak? Even if their release schedule is weak, why would that be sufficient grounds to skip E3?