It's always been pretty common in programming discussions.

Here's a blog post I wrote in 2021 that uses the term shape to describe an algorithm:

https://www.marginalia.nu/log/40-wasted-resources/

And again in 2023, I use it twice in the same blog post both for data and code, and it definitely had no AI input:

https://www.marginalia.nu/log/87_absurd_success/

"Shape" appears to come from JavaScript development wherein an object's "shape" is its structure: the set of properties and methods it is expected to have.

I guess a lot of people use shape, for example to discuss frontend.