Instant level 20 after finishing coop missions?

Someone mentioned this earlier, but I couldn't find any info on it. Is this true that if you finish all coop missions you instantly become level 20?

By the time you finish all the missions you should already be lvl 20. So In a way I guess thats true.

at a certain point, it makes you level 20 if you arent already

edited

Ouch, that's a bit of a spoiler. You might want to modify your post a bit.