Mentioned in  on Core SVN:
Docs: In `wp_schedule_single_event()`, add a note about scheduling an event to occur within 10 minutes of another event with the same action hook.
Created ticket #37455 on Core Trac:
DocBlock of wp_schedule_single_event() should mention 10 minute lock
Created ticket #1140 on Meta Trac:
"Pending" forum reply in stats, but not in topic
Created ticket #1134 on Meta Trac:
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