I have never read where the producers completely ruled out time travel. They did say that the passengers were not in a time warp. (like they landed in a prehistoric era with dinosaurs...lost in time kinda thing) To me, that does not mean that they are not exposed to others who may have the ability to travel through time. The island is in the current time and space that the airplane passengers live in at the time of the crash. However, that does not mean that this strange island does not contain a portal or worm hole that others may be using to travel through. If I am mistaken about this please give me the link to where the producers said there is no time travel involved in this storyline in any sense because I have not seen it.
As a side note: I do not believe a baseball bat blow to the head sent him hurtling back to the future. I just think his being knocked unconcious coincided with his being pulled back, conveniently keeping the producers from having to come up with some big time travel sequence and spelling it all out.