The top video, the rider's only real mistake was target fixation. He got focused on the guard rail while braking for the turn in and got focused on it and steered right into it. We've had discussions on this very video months and months ago and found out the rider was a brand new rider. Speed itself wasn't really an issue as he wasn't even at greater than a 10 degree lean at any other moment on the video. He was probably below or at posted for the turn when he crashed. He just panicked and physically locked up.
As far as the second video, it wasn't a steel plate but a space of road where they had stripped away the top layer of road to do work and then filled it up a bit with concrete and never put a new top layer of asphalt in so it's kind of like a big pit. Again, the rider target fixated on the pit and his steering input came way too late and too passively and his wheel ended up hitting the buffer area or transition area where the cement and some of the asphalt that wasn't fully removed. This destabilized the bike and front end and caused a "tank slapper" where the rider appeared to try to fight the tank slapper and got ejected off of the bike.
That fall could've been avoided by....simply driving over it. A bikes momentum does wonders in keeping it upright when you drive over an obstacle. Hell, I ran over a squirrel and the bike did nothing. I can't imagine a steel plate, or anything a road construction crew would leave in the road, being thicker than a squirrel. Still sucks that he fell...
He tried to avoid it like the car but got in between the street and the line of the plate which caused an uneven surface I think.
Sometimes I feel something like this might happen when lane splitting/filtering. I feel like the bumpers or light reflectors might mess with the alignment of your tires/bike. Anyone care to chime in on filtering?
He could have gone to the far right of the lane and avoid it all together like he originally intended to or do as you say and just gone straight through and have been fine as well. While I have ridden over, daily, a large steel construction plate, it's always a lot more dangerous since steel has a lot lower friction coefficient than asphalt or even cement. Sometimes, these guys put shit in the roads forgetting that motorcycles still exist. Although in this video, you'll see that it isn't a steel plate but a cement patch with a manhole cover in the middle of it. It's either raised or depressed and he got caught on the transition point where the elevation change happens.
When lane splitting, you're generally at lower speeds anyways so you shouldn't really have to worry about hitting a reflector at high speed and causing the front end to violently react. Also when lane splitting, you really shouldn't be riding right on the line itself where the reflectors are placed. You should still be in one lane or the other and not riding the line itself. Riding on, or crossing the line is considered a lane change and requires you to signal as if you were changing lanes.