I'm not an expert on either, but as I understand Extreme Values they generally come in two flavors:
Max (or min) in a given time period, and
Values above a particular threshold (POT, Peaks Over Threshold)
Your alternative seems to be to look at all max values -- or some percentile -- which would still be different from #1 (which would aggregate to one maximum per time period), and would be more different from #2 since a threshold is an absolute number rather than percentile.
Not sure of the mathematical implications, though.
Per your comment, I believe that after the first step EV analysis then fits appropriate EV Distributions (Weibull, Gumbel, etc) to your data, which may or may not be the follow-on analysis that you're thinking of. And I'm not sure how much of the fitting depends on #1 or #2, above, as opposed to something close to that involving order statistics.