I got burned by the shitty circlips on a rebuild at least 25 years ago. The thing that bothered me most was my assumption that the supplier wouldn't send a crappy part that would fuck up my fresh rebuild. I'd say I rode the newly rebuilt bike on and off for about 2 weeks before one circlip popped out at 60mph with a "POP" and a puff of blue white smoke. I pulled the clutch, killed the engine, coasted to a stop and got a friend to pick me up with a van to haul the bike back to the shop. I knew something let go... it was coming back apart.
After buying probably a few thousand dollars worth of parts from this supplier, I couldn't even get the owner on the phone. I was told he doesn't talk to customers, but I could send him a written inquiry and once a week he sits down and goes through these inquiries. Instead of writing him, I just never bought another thing from them.
Originally, when I saw the wire circlips during my initial rebuild I wondered about them, but I thought that they must be OK, or my supplier wouldn't be selling them. I didn't know any better at the time, so I got to tear down a fresh top end 2 weeks after my complete rebuild... and redo the jugs again.
It's fucked up if suppliers are still sending out pistons with those shitty circlips if they are known to fail. Back when I rebuilt my engine, I'm not sure if the circlip issue was well known then, so maybe no suppliers knew the circlips were crap.
Below is a picture of the circlips after one popped and I removed them. Notice the flattened face of one of them...