Hmm. Tell me what other s/t tech that we know of is remotely close to tobi's.
FTG-No Requires a special seal
Summoning-Also requires a seal and usually blood
We know that Tobi touching Naruto is for one of two purposes:
Human Path
Dimensional Transfer
It is much more difficult to transfer any object into a moving dimension if the object is moving. It bodes well for Tobi to grab firm grip then utilize his Sharingan for the transfer.
During the battle with Konan he switched from absorbing the attack to phasing through it:
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This suggests that the act of physically touching the object being absorbed is more insurance than a requirement for the technique. We have seen many links showing tobi physically touching ninjas to absorb them, but no one suggested that it might be a ploy to add stability to the object being absorbed. Tobi could absorb an explosion, which is not a physical object that is touched, but is a force upon Tobi that can be absorbed.
Tobi has the advantage of tangibility. THIS IS THE REAL MYSTERY.