In the lot we tested, most of those seams were just junctions in the mould used to coat them and didn't actually have any depth. They may take a little extra attention while scrubbing but they weren't deep enough to be a hazard. Also most had some form of sturdy cordage inside the silicone cord to reinforce the wires in the case of pulling.

In one particular case, my ~55kg tester hung one of the sturdier models from a pull up bar and picked herself up with it. There were also a lot if nunchuck stunts lol. While most won't hold up to that level of stress, they're more than adequate for the grip strength of human orifices. A caveat to that, if you're worried about size or ease of retrieval anally you can start with guaging plugs. Similar to normal butt plugs they come in sets of 3-12 and have progressively wider diameters. This aclimated the body to a wider stretch.

For those with worries about anal incontinence from guaging, understand that the human anal muscles engage in both directions. So long as you're giving your body time to aclimate to the new size, you will actually gain muscle control and strength from this process. When pared with regular kegal exercises it can make a huge difference, especially for people advancing in age.