I have never pulled a Mini, but did pull a manual diesel Jetta in neutral for years and 10's of thousands of miles with no transmission issues. Just assumed that in neutral nothing could happen. After a faulty Blue Ox base plate design caused the font sub frame to fail, we had to look for something else to pull.
In doing that research, I found out that all manual transmissions are not created equal. There are various ways to ensure that transmission oil gets to all moving / rotating parts. In some transmissions, these systems are driven from the output shafts, in others they are driven by the input shaft.
If your transmission uses the output shafts you should be good to go. If it uses the input shaft then you could have parts of the transmission running with inadequate lubrication.
On another note, I owned a 2017 John Cooper Works Mini. Wonderful car. Unfortunately, someone hit me from behind and at above highway speed and drove me head first into a concrete barrier which stood its ground. Woke up on the hospital but was in pretty good shape considering. The drivers area was almost untouched even though the rest of the car was half its orginal size. For small cars, they are very stout and safer than many larger cars.
Love the Air Force 1 system. Moved it from the Jetta to the Wrangler and still going strong.