Yes, it is odd at best. I just read an article on the step pyramid, and found no reference to grain silos. I did discover that its estimated construction time is between ten and fifteen years. That rules it out as a grain storage facility in Joseph’s time—as did all the other details.
I can’t imagine what Carson was thinking of, to say something like this. I guess he’s not expecting it to get much coverage—and it likely won’t.
The step pyramid itself would not have contained the silos—they would have merely been in the same complex.
I never heard of this association before, but at the link below is an explanation for some peoples understanding.
http://www.arkdiscovery.com/joseph.htm
https://josephandisraelinegypt.wordpress.com/tag/saqqara/