OK BGQ, 10 out of 10, go to the top of the class. You've described the one situation where being ETOPS costs more fuel, that is, where the track must deviate from Great Circle to remain within ETOPS coverage of en-route Suitable/Acceptable/Adequate airports. That will, of course, cost more fuel.
It still remains that contingency fuel for Depressurisation / Engine out remains the same for all transport category aircraft, whether they be ETOPS or not.
Yes gashcan, Depress/Eng Inop fuel is mandated by the regulator when operating in all areas, regardless of the number of engines. The applicable reserves will invariably be specified in the operating company's fuel policy, which must be approved by the regulatory authority as required for the AOC. This covers (for any aircraft) the situation that you describe - "1.5 hrs from destination and the diversion is 2 hours do you have sufficient fuel?"
Of course, it is also a common sense requirement.
Good topic, interesting replies here, getting away from the usual "What is ETOPS" question.
Regards,
Old Smokey