Sector sizes on magnetic hard drives are not fixed, it can be 512/2048 and modern larger drives go up to 4096.
The storage medium and method of operation for a CD is drastically different from magnetic media which is why there are frames, and there are different modes CD's can be written in with various restrictions and levels of error correction associated with each.
A frame for an audio CD contains some error correction information for durability just enough to keep errors from making loud pops or ticks that you can hear. Mode 1 data CD's still contain a bit of correction information because small audio glitches are okay, but small data glitches are not okay. Mode 2 data CD's drop one layer of error correction only 16 bytes of header/synchronization data are required but they become more sensitive to scratches.