OK, maybe I was doing it wrong all these years.
Did it on Hippo at least five times since purchase, on L322 twice, on my wife's Jaguar MANY times (don't remember how many), at least 4 times on W220, and several times on Cessna 210. These are just most recent "hard resets" I've done. NEVER had ANY issues because of it.
From 1995 to 2000 I owned a car dealership (VW, Saab, Subaru), and my service department did that after ANY transmission repair/replacement, and this was actually in the Saab dealer's service bulletin.
I don't have a first hand info on the Jaguar Service Bulletin, but was told over a year ago (on Jaguar forum) by a certified Jaguar tehnician (from UK) that this is a NORMAL procedure in Jaguar dealerships.
Disconnecting the both cables, and leaving the battery out of the loop, WILL drain residual charge, and on most vehicles it will take hours, and in some cases overnight. Crossing the cables accomplishes the same thing in 5-10 minutes (it's NOT rapid, OR violent in any way).
So much so, that service department does it right when they start to work on the car (e.g. transmission), and connect it back when done. Tranny needs to learn the new shifting points, and driving habits, as well as throttle pedal possition. ALL "adaptive" vehicle systems (e.g. auto adjustable suspension settings) need to "re-learn" the driver's habbits, and after so many restarts (varies per model), it's all back to "normal".
Anyway. This is MY take on this, and I am not forcing my opinion down anyone's throat. If in doubt, contact your nearest (factory certified) service department and ask them if and how they perform "hard reset" on the vehicles they service.