Apologies, I was wrong on the weep hole. I should have had another look at my 2018 ATAS muffler, I just had the exhaust off to install Hepco & Becker lower crashbars. Turns out it does not have a weep hole, I do have some discoloration on the swingarm in that area I thought was from that.
I checked and part numbers for muffler are the same for 18/19. It's possible someone drilled that hole, would be ease enough to plug I suppose but may want to check with dealer and verify.
2019 Canadian AT here and no hole, so it's either a country thing or a batch thing. I also noticed the muffler I removed after about 1000km had started rusting in my garage kept at 45% humidity. Some Autosol, ACF50 and 30 minutes later its back in the box.