All fair points.
The "electrically unprotected" cable from the IT to the boat's consumer unit in my case is about 10ft but this is in a secure conduit so unlikely to suffer mechanical damage.
With a shore IT, the "electrically unprotected" cable is somewhat longer and more likely to be damaged being exposed to external elements/mechanical damage.
I guess on balance, in the extreme case of a transformer fire, it's better that it happens off the boat than on it
Is the placement of IT's (if fitted) enforced in the Regulations? Seems like it should be