It got me all confused. Double is the proper way to do it dependant on what type of coupler used. Single shouldn’t be used on brake systems but some argue a male and female connector is fine, personally for the extra 50p that a joiner costs, use one.
This may help and I don’t think the 75 has anything odd - I posted on here another model of car of mine used American and european types leading to much annoyance getting hold of a suitable flaring tool.
http://www.fedhillusa.com/?page=flare