I honestly can't tell for sure, but whether they centralize themselves or not is irrelevant, because...
You dream. Not just in REM, but throughout the majority of your sleep cycle, even in N-REM sleep. The dreams might possess some different characteristics, but rest assured that eye movement still occurs in these phases, even though it might not stand out as much. This is not to say they won't return to their position (whatever is it) at some point before REM, but it would a literal guessing game which wouldn't be any helpful for EILD purposes.
Edit: after reading that EILD description (this is WILD for all purposes), I don't think you should worry too much: I'm not calling the creator a liar, but how does he know his eyes centralize when he falls asleep if he's...asleep? Just focus on the basic steps of WILD and you should be fine

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