We are worried the doing so would simply stimulate new demand for ivory
Assuming the fake ivory is cheap enough to manufacture, this could be a sustainable industry, as well as save wildlife.
That only works if the fake product and the real product are indistinguishable goods. Fake ivory and real ivory are not equivalent; one has value as a status symbol. The cheaper fake ivory becomes, the more of a premium there is on having the real thing.
That's the fear, anyway, and it's not total fantasy. Luxury car brands capture new customers with that exact model. The lowest tier of luxury car is even called the "entry-level" segment.
Experts aren't sure if it would be a problem yet, and are understandably concerned they might simply make the problem worse. Don't rule the concept out simply for vague association with the failing "war on drugs". "Should we flood the market with imitation ivory" and "Should we ban cannabis" are very different questions.
Also, indirect prohibition has shown to be failure time and time again, often being more harmful than not.