Cybernetic horizon can't send dragon

YGO Omega Bugs
2

Not a bug; 'tis more likely a misinterpretation of the card text:

Send 2 Dragon and/or Machine “Cyber” monsters with different Attributes to the GY (1 from your hand and 1 from your Deck);

  1. The Monster Type is put before its archetype as to not confuse people by saying "Cyberdark" Dragon monster, which could also mean "Cyberdark Dragon" monster.
  2. The 2 mentioned Monster Types, Dragon and Machine, are a single group of monster types, hence I formatted them above.
  3. By your logic:

During the Battle Phase (Quick Effect): You can Tribute this card; Special Summon up to 2 face-up “Supreme King Dragon” and/or “Supreme King Gate” Pendulum Monsters from your Extra Deck in Defense Position, except “Supreme King Dragon Odd-Eyes”.

This effect would also be able to Special Summon face-down “Supreme King Gate” monsters and/or face-up “Supreme King Dragon” non-Pendulum monsters.