Is there any way to stop a low-profile desk from racking back and forth?

When I remodeled my house I had left over granite from the kitchen. I had the mason cut a piece for a built-in desk in a dormer. He first cut and polished a piece that wasn’t the right size. I kept it with the intention of building a desk / table out of it in the future. I have now done that and the table looks just like I wanted it to – very minimalist – but there is a slight racking (swaying) side-to-side that I’d love to correct. I don’t see any movement at all between the tops of the legs and the wood when it’s racking, but I have to assume it’s coming from this table-leg connection and not from an unlevel floor. The legs have adjustable feet that haven’t helped.

I bought pre-build metal, rectangular tube steel legs. They’re rated to hold 220lbs each. I connected them with flat-faced hurricane bolts to 3/4" plywood at 62" x 28" to fit under the granite. I then added a piece of 1×6 nominal hardwood across the belly to connect the legs and support the table. Outside of the wood I mentioned, the legs are independent.

With this setup (before the granite), I could sit on it without issue. There was still some racking, but I’m 240lbs. So, adding the 120lb granite weight didn’t seem to be an issue. I now have had the granite just sitting on the plywood without any adhesive. It’s been sturdy for 2 weeks.

Could someone please give me some ideas on how to possibly remove the racking without fundamentally changing the look of the table? If it can’t be done, I’ll live with it like it is.

I have come up with adding flat, angle braces in the corners to possible sturdy up the leg-table connection. I also thought of cutting 62" x 2" x 1/4" steel to bolt directly to the 2 legs to stabilize them from moving independently of each other. Like I said, I could probably add a skirt or some other boards or metal around the outside of the legs to make it not rack, but that would defeat the purpose of what I’m trying to do since I wanted a desk that I could work from one side and someone else could work from the other side.

Any help would be greatly appreciated. Thanks!