For those of you using non-Samsung phones who are encountering the issue where you can only read the most recent SMS in thread. I can confirm that switching to Textra allows you to view all past messages when a new one comes in.
You will still not be able to see history (other than what is sent by the watch) when not viewing a new message.
You will still not be able to see history (other than what is sent by the watch) when not viewing a new message.