That is a myth... and not a maybe myth.
Snakes need 3 things to recognize a prey item....
1) smell
2) heat
3) movement
I feed 45 snake every week in their enclosures and have never been mistaken for food.
Snakes need to be "warmed up" to a feed, meaning they need cues, and a process to get them into feed mode. Randomly reaching in to tend to them will not get you mistaken for food.
Reaching in when your snake is in feed mode and you smell like a rodent, THEN you stand a good chance of being hit.
I never handle any snake on feeding day, and how you are feeding you do run a good chance of getting tagged, which is what you seem to be trying to avoid.
Ironic, eh?
Bruce