Personally, on most models I own, or have owned in the past couple decades, they came equipped with a 'rod lock' or 'cam lock.' A few, however (mainly Garrett's) haven't had a rod lock. I recall many of the Tesoro models from the '80s and '90s didn't have a rod lock, and that would have annoyed me anyway because too many of their models had the holes punched out of alignment and the search coils were canted. a rod lock would have held them in a canted position anyway. Some makes I have had in the past, like many Compass models, didn't have holes to secure the rod in alignment anyway, and their rod locks were often poor at holding the rods in line with the housing, or from keeping them from collapsing.
So, sometimes they wouldn't serve a lot of purpose, and sometimes when they were used they didn't really do a great job. let's keep in mind, too, that cam locks/rod locks haven't been a bit item on Garrett models anyway and I haven't see that as a major reason for complaint in the past. Also, this is a unit that's good to 10 feet so some are going to get a fair amount of sand in the rod system. Yes, I have used some brand s of water units that have rod locks, but I've encountered a lot of them used, gently used, or handled them as customer repair returns that were rather bound up in the rod lock due to sand.
Sand/fine dirt or grit doesn't just come from beach hunting, either. I have a good friend and hunting buddy in Utah who seems to attract 500X the amount of dirt and grit and crud in her detectors that I have in all my life! So, maybe it's not such a big deal, and none of us will really know until a good number of them are released and used in the field for a while. If a lot of folks gripe about rod wobble and the need for a rod lock, maybe Garrett will listen up?
Monte