These cases are old and this cannelure seems to be a failure point on the case. The case eventually cracks at this point.
Do you have or have you seen any of those cases that cracked at that point??
also, are they balloon head, or solid head cases??
Take a light and take a good look inside the case. Use a tool and drag it up the inside of the case, looking for /feeling for a ring inside the case. If the cannelure does not bulge the interior case wall, then its an ID marking and highly unlikely to be a failure point.
A case cannelure that actually creates an indent in the case is usually to serve as a stop for the bullet base. I have brass like that, specifically some old .45ACP brass. The case cannelure prevents bullet setback.
I also have a bit of brass that has two cannelure rings (.38SPL) in the middle of the case. These are knurled rings that do not intrude into the case interior and I'm told were simply put there as an ID on the cases indicating that they were, or had been loaded with target ammo.
If you have a chance, look at some GI .223 BLANKS. They have a cannelure just above the head of the case. Its a marking who's function is to ID the case as being made as a blank. SO, even if someone trims off the brass crimp portion, its still evident the case was made to be a blank.
A cannelure on the case wall is not on a portion of the case that gets "worked" as much as the case mouth. Expansion on firing, compression during resizing. That's it. Even if it is a thinner spot on the case wall, its not worked any more than the rest of the case and it almost never fails at that point.
Also consider that 50+ years ago all the way back to early metallic cases, the reloading "service life" of a case was not the makers highest priority.