There is a fairly recent video of him repping one plate. Some podcaster was clowning him for his absolutely shit form, legs flailing all over the place. I agree with you, if someone can bench 3 plates they have the form down better, especially on a lower weight. And if he doesn't have much lifting experience how can he bench 3 plates, would be extremely unusual to say the least? Lying about lifting related things is real crime for me LOL. Seriously, what kind of person does that? 
I remember seeing this 3 plate vid and thinking, ok maybe. Now that I've seen the 1 plate one and I've been reminded of the older one, no.
There's that, for sure.
And look at the video Coach posted. The guy unracks the weight with zero assistance, and the bar goes off-balance because he's pushing harder with one arm than the other, and he has zero arch or setup.
NOTHING about that looks like a three-plate 1RM attempt.
But also, and I think that this is more conclusive proof, nobody on planet Earth has
ever benched that much weight, with that technique, what a physique that looks like that.
I've seen IRL some big deadlifters and squatters who barely look like they lift, but I've never seen anybody bench as much as two plates with skinny noodles for limbs. And literally everybody on YouTube who benches three plates is at least twice as muscular as Hegseth. He just doesn't look like a man who can pull off a lift like that. Why is he lying about it, though?