Yes, which is why experimenting with features on the standards track is okay. At a certain stage it becomes less likely that the feature will change behavior.
The problem arises when the experimentation is done with entirely new features that the browser wants to push (features which haven't been discussed and somewhat settled on with other browsers). If they aren't behind a flag, sites start using it, and then you have to support the legacy syntax forever.
clip-path is on the standards track. It's not going to change much. So browser vendors exposing it by default is fine.
(However, if you're building an experiment using these, at least test in other browsers and put up a warning that it won't work in some browsers. A lot of the interior issues today are because folks only bother to test in chrome. Ultimately this means that all browsers have to copy Chrome bugs to make things work.)
