I am certainly not able to answer in any official quality, but I would say that you are correct and the intent is that greater magic siege engine is touch range.
I am only surmising here, but my observation is that the magic siege engine wording was based upon the magic weapon line of spells and was cut-and-pasted with only the scarcest of proof-reading. As such, rather than basing greater magic siege engine off of magic siege engine like most people might think, instead magic siege engine was copied from magic weapon and greater magic siege engine's wording came from greater magic weapon, which would account for the discrepancy. But that is just an observation and guess on my part.
Either way, I don't see any logical or mechanical way that a range of close would apply (unless the target line was completely in error, which doesn't seem the case).
