Why did Siri open Seayora when I asked it to edit or unsend a message?
Changing what you already said is something only you should confirm, so Siri gets it ready in the conversation and you tap to finish. Sending a new message and marking a conversation read are the things Siri can finish on its own — the same two things a notification lets you do from the Lock Screen.
From the guide Siri, Shortcuts, Control Center & App Shortcuts.
Sending a message with Siri
- Your iPhone must be unlocked. Siri asks which conversation and what to say, and reads back where it is going.
- Siri says "Sent" only once Seayora has the message. With no signal it tells you the message will send when you are back online — it waits in the same outbox the app uses, and goes on its own.
- If Seayora refuses the message, Siri says it could not be sent and asks you to open the conversation to see why. It never reports a message as sent when nobody received it.
- It goes through exactly the same service as the Send button in the app, so everything that applies there — who you may message, blocking, the conversation's rules — applies here too.
Read the whole guide: Siri, Shortcuts, Control Center & App Shortcuts