Honestly, why not? It's quite likely there has been a decent amount of information passing back and forth between NASA and various private space companies - there isn't a sane reason to require everyone to make the same mistakes that you've already learned from. Additionally while releasing rocket specifications probably won't result in any at-scale replicas it's a good way to feed the hobbiest community and possibly get some neat ideas back.

There are some components of rocketry that deserve careful consideration in sharing (i.e. rocket fuels) but a lot of those have mostly leaked at this point and the government has other reasons to limit their production and thus limits the supply of chemical components.

Much like with software there are going to be some secret components related to communication and the like - but those can be cherry picked from the information and deliberately hidden... similar to how most software teams don't check all their private SSH keys into public repos (usually).