>>- Some enclosures have an LED activity indicator which is cabled to the USB/SATA bridge board via a 2- or 3-pin header. Often that cable has to be disconnected, then reconnected when replacing the hard drive. If you plug it back in incorrectly it *might* cause problems:
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>I haven't had to do that when putting other drives in (they were already formatted though whereas this one is a brand new unformatted one).
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>>- Best case scenario is the design may not care, the enclosure and LED may work fine either way
>>- Most likely case is the enclosure would continue to work except for the LED
>>- Worst case is hooking it up backwards causes the enclosure to fail

Here I was talking about enclosures which have LED indicators on the front or side, some distance from the rear circuit board. Those enclosures have a cable that runs from the LED to the circuit board. The cable is only just as long as it needs to be. When replacing a drive in that type of enclosure you have to pull out the sled a little bit, disconnect that cable from the header on the circuit board, then you can fully remove the sled. After replacing the drive, you push the sled most of the way back in, reconnect the LED cable to the header, then fully insert the sled.

The circuit board header the LED cable is plugged into is typically not keyed, it's possible to reconnect it the wrong way. If the design isn't tolerant of that possibility then it could conceivably cause the enclosure to fail (scenario 3 above).

If you have an enclosure like this, its documentation should indicate how the LED cable should be connected to the circuit board.

This possible issue has nothing to do with the formatted state of the new drive you're installing.