I believe those are alternate connection points in case there isn't room in the battery box to attach from the top. (There's no way I could hook it up from the top like that on my motorcycle- It's a tight squeeze)
They would provide an excellent place to hook up your tender pigtail.
Chances are good that the battery you have was made as a universal fit. Back around 2000/2001 side terminal batteries were being promoted. If the maker intended for their battery to be compatible they would have included side terminal capabilities. The fact that it never really caught on is irrelevant. Use the extra connection point as you wish. To me, a tender connection point sounds like a good thing to do with it.