I didn't take it that way either - its just a HUGE misconception about the whole eye dominant thing !

Squinching an eye, or closing it does 3 things gauraneed - #1 a loss of field of view #2 all loss of depth perception and #3 you're doing something 180 degrees different than your normal hand/eye is use to

it can work, or course, through lots of practice, but its my opinion you're much better off to swim WITH the current than against.