Honda just pre-wired the ground to cut down on Winch install. They want us to take off a bunch of body panels to install that ground. To be honest the flat rate @ 4.5 hrs is about right if you do it the way they want you too (take front fender off, etc.) But aan good tech cheating the system could do a 2016 model in about 2. I've got mind under 2 hours but that''s because I've done several and know the ins and outs of installation. With the ground ran, realistically I can see it taking maybe less than 1 to 1.5 hrs.
Honda never recommends grounding to the battery post to cut down on the risk of a loose cable causing issues with voltage to ecms, etc. I dont like grounding to the battery post for this reason as well. I dont know how many issues can be traced back to loose battery cables because of piled on accessories.