I suggest someone might be blowing smoke up your brother's posterior. There is nothing about a 2016 SESG that would make installing heated grips difficult, assuming the person doing the install was even reasonably competent. And yes, people on this site have had heated grips installed on their 2016 SESG's. It can be done by purchasing a kit from the accessory catalog, or by purchasing the production parts used on the CVO Limited. The SESG already has the same front wiring harness as the Limited btw, so it isn't necessary to run wires all over the place as indicated in the instructions for those kits in the catalog. The connections can be made to the existing connector up near the steering head area, just like on the Limited.
Jerry