Perhaps they meant seekable when compressed? As in the header for each object has the compressed length of object? Presumably in a meta data header with name, c

Perhaps they meant seekable when compressed? As in the header for each object has the compressed length of object? Presumably in a meta data header with name, compression format, claimed uncompressed length, date, etc. Personally I'd like a tool that lets me extract files from TB size archives easily without decompressing everything. Only virtual disk images seem to have that random access functionality. There are ways of using gzip/bzip/xz that use sync points, so you could produce a compatible archive that allowed decompressing metadata bits, though it would suck for many small files.