Encore preview is an emulator, like computer DVD players, that attempts to predict what will happen when a disk is played on a set top DVD player. It has always had issues with some predictions not being accurate. Some inaccuracies are like this one: Encore preview does not work, and a burned disk will. Others are the opposite; it works in Encore preview, and not in a DVD player. The point to be made here is that you cannot rely on Encore preview. You also cannot rely on computer playback of a built image or folder. And, in the end, you cannot rely on playback on one DVD player - some disks work on some players and not on others.
The issue in this thread, and old one about CS4 when CS4 was current, is not the problem you are presenting. The loop point sorta works in Encore preview, but has a glitch. Such delay or gaps may well occur in playback in a DVD player, but there, they vary based on the physics of the disk, the particular player, and where on the disk various files are located. And for some purposes (bluray primarily) Encore has introduced gaps where it should not.
The bottom line is you will need to test to see what is true for your project. But I would not assume the gap will be there when you test a burned disk.