From Reddit: NO level sync when entering a dungeon with less that required players!

[Bhuni]

Players Need Incentive!!! I cannot stress that enough. The majority of the playerbase will not opt to level syncing if the gain is the same as doing it with max lvl/ilvl... The "challenge" for the sake of a "challenge" is not enough. With overcoming a challenge, players want to see the fruits of their labor rewarded. No one cares about bragging rights. You might as well not even implement the lvl sync feature...

The reward is becoming better at your job by challenging yourself, that's a good enough incentive for me.
If you wanna put on shiny show in Mor Dhona there is going to be plenty of stuff to swag from other upcoming content.