reasons:

• unix domain socket listener only
• can rewrite client requests before using config files
  • thereby inject workstation IP address into add_onion command (T562)
• can rewrite replies by Tor using config files
  • thereby prevent the workstation from learning the hidden service private key
• less work than implementing the same with Whonix control-port-filter-python
• sharing code with Tails
• written in python3

disadvantages:

• no configuration drop-in snippet configuration extension feature, see T576

• https://www.whonix.org/wiki/Dev/Control_Port_Filter_Proxy#tor-controlport-filter_by_Tails
• https://git-tails.immerda.ch/tails/tree/config/chroot_local-includes/usr/local/lib/tor-controlport-filter?h=feature%2F7870-include_onionshare
• https://git-tails.immerda.ch/tails/tree/config/chroot_local-includes/etc/tor-controlport-filter.d?h=feature/7870-include_onionshare