Hmm... this reminds me of my diligent efforts to preserve my night acuity while on some road trips over the past 20 years. First I would close the left eye as cars passed, preserving it for afterwards.
Then I decided my normal-size nose was a bit in the way. Now I close my right eye.
From a strictly tactical perspective, the momentary closing of both eyes appears to be fine. Target is identified, and if done "instantly" enough, you won't miss anything that you would be able to react to anyway.
But if you've ever been a bit lost after the blank-out of a single-lens reflex camera taking a photo shot (I have), then maybe the one-eye technique may be better.
I'm not going to be able to get out soon. Care to repeat your experiment using the one-eye closing idea? I'd suggest closing the NON-aiming eye, as it has a wider field of view, the better to see the Goblins with.
Gotta be careful with those big bad wolves...