That was my thoughts on the stock sending unit location as well.

The adapter just slides up on the oil filter threads and the threaded part you see in the middle is a "nut" that tightens down on the original oil filter threads to attach the adapter. This design allows us to install the adapter at whatever angle we need to make sure the sending units don't interfere with anything. As opposed to having fixed threads and twisting it on like a filter -- you'd have to leave it wherever it happens to get tight.

I check it every oil change (three times) and haven't found it loose so far.