Its working that way since day one the LFD system is implemented, and have been posted several times here, if I am not wrong.
You get extra 1-3 levels on the linked chars off the LFD completition reward, granting experience, worth 2-3 levels in the 15~50 range, and ~ 1 level in the 50-thies.
For example, single DM run on lvl15 with heirlooms and quests grand 6-7 levels, so you are ~lvl 22 when you finish it.
Past 60 the experience pool is expanding alot, so you need 10+ dungeons till 70. Same applies to WOTLK content.
Thanks to it you were able to grant ~470k exp on level 1 toon (before it was hotfixed ofc.)
http://www.ownedcore.com/forums/worl...any-level.html (Get 100k EXP on any level)
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