That’s the problem though, getting the email with a copy of the recording may be the unwitting participants first indication that the call was recorded without their knowledge or consent.

Otters defense is that it’s up to their users to inform other participants and get their consent where necessary, the claim of the lawsuit is that Otter is deliberately making a product which does not make it obvious that the call is being recorded, and by default does not send a pre-meeting notice that it will be joining and recording.