It’s an iOS/Webkit bug. I had a cumbersome workaround for that, but it wasn’t worth fixing it that way as it was complicating things a bit too much and most people probably never notice.
I hadn’t noticed them before, but if you take a screenshot and zoom in a little you can see them. Once you’ve seen them you can’t avoid them. I’m not sure I would say they are jagged more like extra pixels. (iPhone 12)