Hmm, I really don't see it. And I don't see how people compare Jonas' vocals to Maynard's. I always thought Jonas' were so unique and haunting. Actually, here is part of a convo I had with Jonas a few years ago...
IRC operator: jonas, how many times do you sing one song in studio
Jonas: i usually sing the song thru a number of times and then try to nail it. i usually go back and correct shitty things as well.
Me: you have such a great voice. it's so haunting. your lyrics really harmonize with it
Jonas: yeah, i think thay're cool but i have a bit of a problem with the vocals.
Me: is there any specific reason why you stopped with your growls?
Jonas: my growls... disappeared
Me: you just woke up one day and realised you cant do them?

Jonas: no, i tried to do them but it sounded like shit.
Me: aww, poor guy
Jonas: we decided to drop them when we started to work on 'discouraged ones'