Yeah, the metal knitting solution makes the most sense for all use cases - in military camps, buried with women, etc. What sold me was the story of a woman who saw one and immediately knew how to use it. It explains the different sizes of the pegs and the holes in the middle, as well as why they never showed up in historical documents. The shape is clearly a nod to mathematical/religious values, but not required for its actual purpose.
But chainmail was a thing, so how did they manufacture it without knitting? Maybe “knitting” is just a way of describing this, while the knitting you're thinking of is specifically knitting involving textiles.
Chainmail is made from individual rings. Romans made it from punched out metal rings alternating with rings made of wire and then ends of those rings made out of wire together. Not really too much riveting you can do with textiles. Well maybe plastics, but they did not have plastics.
