1) both videos were about TNGA-F vehicles.Neither video you posted was about the 250 or official from Toyota. I've seen the photos you are talking about... Not sure how you derive that assumption.
2) both videos had Toyota engineers speaking to the host, clearly with permission from their bosses at Toyota. These interviews were not unauthorized.
3) Toyota engineers in a video that watched (I think it was one of those two) said that the TNGA-F Platform allows them to scale up or down the gauge of the steel in the frame as needed.
4) Toyota has confirmed that the Tacoma, Tundra, Sequoia, Land Cruiser 300/LX600, and GX550/LC 250 will all be built on variations of the TNGA-F frame. These vehicles have different wheelbases and different weights, so it logically follows that they will have different loads and thus have different strength steel in the frames.
No, I’m not saying that the LC 250 frame is going to be “weak”. I believe the LC250 will be lighter than the LC300 and will have a lighter frame as a result, just as I believe the 2024 Taco will have a lighter frame than the 2024 Tundra. No, this doesn’t concern me. I expect the frames for the LC250 and 4Runner will strong enough for anything I might do.