Some of the bigger areas that "encourage" stealth (via high grass) feel like there's no real purpose to be sneaky since if you get caught, you're stuck in the middle of a massive open area surrounded by dudes instead of just marching from one end to the other like a typical Nathan Drake death machine. I tried stealthing the second encounter in Chapter 13 and just gave up since it a) apparently was not meant to be completely bypassed since they straight up stop giving you high grass halfway through and b) is so much easier to just shoot everyone than risk stealth. I've enjoyed the stealth in smaller encounters like mini outpost areas in Madagascar, but otherwise it feels like it does more harm than good.
High grass isn't the only means to stealth, in fact on harder difficulties it is the less effective method of staying hidden whilst traversing a large area of a map. Rather, use your environmental surroundings, elevation differences, pillars, ledges, buildings, windows, walls, cover, hanging off or behind stuff etc just as much if not more than high grass. If you watch the video of how to get the ghost trophy in Scotland, this is further highlighted. Also, use water (underwater swimming) when you can as well.