a bubba burger (grocery store frozen burger) has 90mg sodium (https://bubbafoods.com/nutrition/bubba-angus-beef-2lb/)
a beyond burger has 310mg https://www.beyondmeat.com/en-US/products/the-beyond-burger
They are lower in fat and total calories but they are obviously more processed = salt. Even a mcdonalds burger patty (without the bun) has less salt.
McDonalds quarter pounder has less salt per oz, but the Big Mac / basic burger patties have more salt per oz or per protein gram.
https://www.mcdonalds.com/us/en-us/about-our-food/nutrition-...
Not everyone cares about processing or salt. And like the OP said it's not a comparison to a bean burger that matters, they weren't going to chose that anyway, it's the comparison to real meat