I fail to see how battery orientation makes any difference if we're talking about a device with no spring.
Of course if there's actually any logic and/or science behind this claim we'd all appreciate seeing it rather than sarcastic comments.
Standard Orientation:
-----------------------
+[[[[[[[[[[[[[[[[[[[[[[[-|
-----------------------
Reversed:
++++++++++++++++++
-[[[[[[[[[[[[[[[[[[[[[[[+|
++++++++++++++++++
if the sheath on the battery, the colored plasticy part becomes damaged, the casing of the battery(-) could come in contact with the tube of the mod(now + because of the reversed battery).
this would cause a hard short
A hard short looks like this(fast forward to 1:58):