This is what Focal said about it (in October 2018). You are right, it wasn't the 2020 revision specifically that they fixed it, but they claim to have identified and fixed an issue with voice coil fragility at some point after the initial release. But as you say, there do seem to be still a high number of failures.

>Regarding defective Utopia drivers, as already mentioned in the first pages of this thread, we experienced a voice coil fragility during early production batches. Not all headphones from these batches were affected. This problem which caused some drivers fragility has been identified, analyzed and fixed. We managed to take on defective headphones returns, but some units could be left on the market.

>As this issue is identified by our Team, we have informed our distribution network and they know how to proceed in case of defective drivers. Indeed, all defective headphones under warranty (according to local warranty policies) will be repaired free of charge by the Focal Team (the driver will be replaced). Which is why we strongly recommend you to contact your local dealer (specifying the serial number of your product and attaching the invoice) if you are experiencing any issue with your headphones to ensure After Sales Service. Please note that the serial number and the invoice are compulsory to track your headphones.

>The official warranty of Utopia, Clear and Elear headphones is 2 years by default. There are then specific cases in some countries for potential extension, please contact the local distributor to know the local warranty policy.

>In conclusion, we are aware of this situation and will do our best to fix all defective headphones. Be sure we have reinforced our quality controls.

https://www.head-fi.org/threads/focal-utopia-general-discussion.811273/page-590#post-14515753

I did see that post about fixing the voice coil. I think if I did end up with a failure on one of mine out of warranty I'd try a local/DIY repair rather than Focal, because they reputedly charge an absolute fortune to fix them (like literally thousands of dollars to fix a Utopia driver). Which is outrageous... but they do sound good.