I checked my PC's MAC prefix against the list in the CSV. It was in a block allocated from 2001, but my machine dates from 2017. Not sure how useful this is.
Definitely would like for people to correct me if I am wrong. But I believe as a manufacturer you buy blocks of MAC addresses, if you are one that makes networking devices you probably would buy many blocks and use them for a very long time.
You are correct. The date of allocation doesn't indicate the age of the device, just the age of the allocation to said company.