Yeah thats to prevent bowing.
My 55g I got has a snapped brace, and terrifying finding out when I first filled it, it bowed and was a major break-risk.
I used a glass panel and aquarium silicone to reinforce the centerbrace.
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I probably could have done a neater job, but it was a heck of a nightmare as I had transferred the fish and everything to it before realizing it so had to keep it only 1/4 way full for a few days to let the sealant cure fully and securely.
But it works.
I will say with your centerbrace, as long as it is not snapped and the tank doesn't bow when it's full, it's doing its job.
It's a matter of force being pulled against the brace where it needs to hold.