Thank you for making a bug report!
As shown, and mentioned by Lyris, this is functioning as intended.
Gozen Match’s text reads: “Each player can only control 1 Attribute of monster. Send all other face-up monsters they control to the GY.”
This means that at the point of Gozen Match resolving, you must send monsters from your field until you control only 1 attribute. Since Dinomight is a water, and Ignister is a Fire, it is asking you to send 1 of the two to the grave so that you control only Fire or only Water monsters.
If you were to instead have Rivalry of the Warlords, you would be able to keep both monsters on field, as Rivarly limits you to controlling only one TYPE of monster. This would mean the card would not care what Attribute the cards were, as long as they were both the same Type, in this case being Wyrm.
If you agree with this statement, please mark this as the solution and the thread will close 24 hours after the last post is made.
If you do not, please let us know so that we can help you understand the interaction.
Once again, thank you for helping make Omega a better experience. If you find anything that you do not agree with, understand, or believe is a bug please let us know by making another bug report or posting up on the Discord server in the #Rulings channel of Duelist Unite.