It's crappy, but most of Microsoft's policies tend to be like that. It benefits them, though, so from an internal business perspective you can say it's "alright." All it means is that XBLA games can go to PSN at some point, but not vice versa. It's a weird policy, but it ensures that they can either get exclusivity for a short time or day and date.
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Simplicity is the ultimate sophistication.