I don't disagree that people tend to set requirements far and above what are required, but that may also be due to those people having bad experiences. If they seem unreasonable for what you believe is necessary for success there's a straight forward way to do something about it.
You're asking me why in a hypothetical situation wow gold people are asking you for Proving Ground medal achievements in addition to raid achievements? That's an assumption, first off, although probably a correct one. Well, one shows you downed a boss, which has no context for what you contributed. Maybe you had a guild carry you or went AFK? Proving Grounds show some level of ability, devoid of other factors outside of your own.
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