Yes, Encode::FB_WARN, Encode::WARN_ON_ERR, and Encode::FB_QUIET all produce fatal errors for me. But FB_DEFAULT does not:

23:20 >perl -MEncode -le "print $Encode::VERSION; decode( q/UTF16-LE/,
+ $f = qq/\xff\xff/, Encode::FB_DEFAULT() ); print 'bye';"
2.47
bye

23:23 >
[download]

:-O