I would think the number of launches that could put an object into such a strange orbital state would be pretty small.
Given that roughly 100 space launches are conducted annually, and that the lower stages of multi-stage rockets can be regarded as independent celestial bodies, and that such independent celestial bodies can also break up into multiple smaller bodies - I'm not surprised.
After all, some lower stages of rockets have entered into stable orbits around the Sun.
Regards,