Area Heals have buffer costs?

So I had buffed this level 3 with that area combat evasion ability (don't recall the name), maxing out their buffer.  Then I proceeded to heal it.

"Buffer is full"

Nowhere in the ability does it say there IS a buffer cost, nor it doesn't seem...logical..for there to be one.

I discovered this a while ago and tested it with a friend. Oddly enough if you use Buffer Overflow on someone to max out their buffer they can still heal themselves. It's only maxing out your buffer with beneficial buffs (And not Buffer filling attacks) that does it.