Giving one hit to the final boss made sense for testing the ending, but why the WFZ boss? Unless there is a difference in the WFZ cutscene nothing springs to mind, since they had level select to get past that, anyway!
Probably to test the transition cutscene from WFZ to DEZ. That boss can take quite a while to beat if you're not invincible or anything like that, due to the unpredictable behavior of the spiked platforms.
I think I've got it, maybe they were testing out for the "black-screen" bug after beating WFZ? BTW: Right there, after the boss, there are three rings in all betas, but in the final they aren't there. Now that's useless rings!
