It's obviously hard to critique a study that hasn't been released, but I [again] find it bizarre how the "introduction" and "conclusions" in the abstract you linked seem to be asking two separate questions.
The intro says "This trial investigates whether the use of face masks in the community will reduce wearers' risk of SARS-CoV-2 infection." (emph. mine) ie. if everyone wears masks, does my risk go down? This seems like the correct question to ask. But then the conclusion says "We will study whether a face mask protects the wearer of the mask against SARS-CoV-2 infection" which is a different question entirely!
If what we have been hearing over the past months is true (masks provide marginal protection for the wearer, but catch a significant portion of aerosol droplets & therefore protect society against the wearer) - I would expect the answer to the first question to be "yes" and the second to be "no"!