I was under the same impression, but it seems to work now. I'm using the latest lr-mame2003, compiled from source, and tappera.zip as the ROM. In the past I believe the controls didn't work, but now they seem to work. Maybe it is related to some of the changes from December? https://retropie.org.uk/forum/topic/2889/mame-development-lr-mame2003-updates