Unless that is an old…
Unless that is an old vehicle that he barely drives it should be covered under the 3 yr warranty. If the batt is healthy he doesnt need to replace it, it is just what the service advisor is advising him do. Also the picture is wrong it is a small 12v boat battery.
My Advise
IMO, if under warranty have them change it out FREE before your 3 year is up.
If it is acting funny plan to get it changed out, the last thing you want is to be stranded away from home trying to open the lid, remove clips, to remove the battery to try to find a replacement as I mentioned it is a boat battery so it is not carried widely and dealers would sometimes need to order it in. I've seen people change it out for other small car batteries as you can adj the backet to hold a slightly bigger battery.