The chard greens definitely have a different consistency than regular beet greens. The chard is officially Beta vulgaris subsp. vulgaris, Cicla-Group and Flavescens-Group - while Beets are just Beta vulgaris. I like beet greens, too. It's kind of like the Wild Field Mustard (Brassica rapa) that has been bred into Bok Choy, Napa Cabbage, Rapini broccoli, and Turnips! That's a wide variety.

Those stalks would be good in the same mix as I use for Pickled Hop Shoots, for sure! I like them for Bread and Butter Pickles, too. I hope you can find some beet greens! But in their absence, the younger leaves of chard are more like beets than the bigger, older leaves.