Right now, in the project page, the 2 build forms available (the one at the top of the page and the one in the Targets section) are reusing a single variable and code path in Angular. The side effect of this is that, whatever you do in one is replicated in the other. This behaviour is quite weird, and should be removed at some point.
The fix is merged into origin/master
verified on master:49547a6d6dead6c9e9c8c209afacd9edc6a9bd5f