No it does not have to be an infringer. It could be a supposed infringer who is doing it for someone else. Someone who wishes not to be "known" to the public. That could be a bigger player/infringer or it could be someone who stands to benefit in delay. That makes me think of DL going to Europe and having "secret/private talks/discussions with that big company. I don't know how a delay would benefit TPL but this ride has been full of mystery and surprises. Anything I or others can think of seems possible to me. The question is how likely? I just hope the USPTO does throw out this request because they are done with this matter once and for all.