It looks at least like you have the mobility to maintain your back position at the bottom of the lift... at least if your form with just the bar is the same as with some actual weight.
Here is what seems to happen though.
As you add weight, your body is going to shift to a more "advantageous" position to actually move it. For many people, you see the hips rise first, then the bar starts moving. Over time, as people learn their own leverages, they just stop lowering their hips so much to start, and instead start at the higher hip position.
There's nothing wrong with that in my mind.
Since your video only shows your form with a light weight, it's not really clear where your hips will be once the bar gets heavier. If your hips start higher, you may actually have the mobility to keep a good low back position and keep it from rounding very much. You may not.
I'd just keep making videos of yourself as you add weight, and compare between them. If you start hurting at all, I would look at the video and see what's different between the last video where you didn't hurt, and the one where you did.
From a long term standpoint, it may be better for you to try and learn a more sumo-style pull and keep your torso more upright. It's not really the same movement and doesn't build muscle in all the same ways, but it might be better for your back in particular.