Hello!
Thank you for making a bug report.
Dragon’s Soul is correct. This is functioning as intended.
You are attempting to bridge a card with 2 matching properties, not “Exactly 1”. Because of this, it is not a valid target for you to add as Shinonome the Vaylantz Priestess and Saion the Vaylantz Archer are both water attribute and spellcaster type monsters.
If you have any questions, please feel free to ask any questions in the #rulings channel on the Duelist Unite Discord server.
Once again, thank you for the making a bug report and helping YGO Omega be the best it can be.