Pos Indonesia also did this! If you get to know the numbers on those stickers (I’d always left the post office as soon as I hand the postcard over, so I never see the post worker sticking it behind the counter), you can track it on their website! (Works for domestic postage, so basically, all domestic postage are trackable by default, even if using stamps, I don’t know for international sending).
Unfortunately, up until very recently, the stickers aren’t really easy to peel off, and they stick it everywhere! Even on international mails and postcards incoming from outside Indonesia! And sometimes the workers don’t really care where to stick it, resulting in issues like this: Calling for help : Indonesian Post Barcode Sticker