Quick and dirty…you're right on both counts.
Factory clear coils were fabulously asymmetrical and frequently exhibited hot turns or leads. So a top-wick hid that.
Did they know the coils were that poor?
These coils were frequently not symmetrical within the assembly (cup) either. So a top-wick helped insulate the coil from shorting on the cup's top cap (chimney).
But the primary functional purpose of the top-wick was to fill the gap that often remained in the slot above the wick itself. Although coils loosely matched the silica diameter they didn't really match (otherwise it just would've been nigh-near impossible to thread them). So the "flavor" wick filled that gap deterring flooding and over saturation. On the other hand, these overly-hot often shorting coils were
cooled by the top-wick which somewhat improved flavor, i.e. less dry hitting from scorched or cooking wick spittin' at us. That is, if you like refried beans.
All's well that ends well in that the tensioned micro and install methods solved these issues here…
Protank MicroCoil Discussion!!. Details and more answers there if you need. Glad to help.
(Love the tag line TB.)
Good luck all.