Credit where credit is due to Sircalum (for posting the link) and to Matt Moneymaker (for offering an alternative explanation for this film). Everyone here seems to be accepting, at face value, that this new film was shot before the P-G film and was a rehearsal for it.
For those who can't (or haven't) read MM's Facebook post, he posits that the new film was shot after the P-G film and was an attempt to recreate the encounter. Why? One reason suggested by MM is that Al DeAtley wanted to have a longer film to show and - let's face it - the P-G film as originally shot is not all that good. So perhaps Al DeAtley and Roger Patterson (and Bob Gimlin, if that's him in this film) wanted to have more film to show on the movie circuit and experimented with a quickly bought (or made) costume to see if they could get something useful. If so, this would have been done within weeks of the P-G film while Roger still had the rented (and misappropriated) camera. Alternatively, Al DeAtley could have been trying to prove to himself that the P-G film wasn't a hoax by trying to recreate it.
Only pointing this out because at this time, we don't know when the film was shot. We know when the film was manufactured, but we know nothing else about when it was used, or when it was processed. So if the film Capturing Bigfoot is labeling this as a "trial run" they have not, at this point, laid an adequate foundation for doing so.