I have the same issue, this was changed some time ago, and is quite annoying actually. Hopefully this will be fixed soon, but is has something to do with the underlying JAVA libraries used for this purpose. There are some tickets on this already available:
- https://lucee.daemonite.io/t/filegetmimetype-recognized-mime-types/1026
- [LDEV-390] - Lucee
- https://luceeserver.atlassian.net/browse/LDEV-1549
So the Lucee-people are looking at it, but not solved for now.