1. The actual filehandle to the compressed file my class reads is opened ':raw', yes. I'm not sure where else it would make sense to do this. If I try to binmode the tied filehandle, it just tries to find a BINMODE method in my class, which I would have to define myself (probably as setting the mode of the compressed filehandle as I've already done).
2. I'll try to generate a minimal tied class that demonstrates what I observe. If I see the same thing, does this seem like a bug or a feature request? Would they both go to the same place?