They did not, that is what Developer Previews or betas are there for, to find all the bugs, since not even Apple can find them with their resources.
Or do you really think, Apple releases DPs or betas for the general public in order for that general public to use a DP or beta as their main system?
Come on, if you are a developer, you would understand that, but since you are not, and got a copy via third party channels, you shouldn't complain, as it was your choice, to install a beta version of a product.
Anyway, why not report that bug to Apple?