I don't think serial numbers would help in this case, as the converters are stolen, precious metals extracted, and then those metals are sold. The bit that would likely be stamped with a serial number is likely discarded.
Unless you're cool with the thefts that are going on, or think any government regulation is "overstepping."
Strawmanning anyone who disagrees with you makes your position look worse.
The grade isn't as pure as industrial processes, but it isn't too bad. Likewise, while the yield isn't good, even if you collect 50% the value is high enough.