I'd never change that setting, so mine definitely defaulted to the shared vault. There could be any number of possible reasons it set that as the default, but my guess would be the order I migrated vaults over from the good old days where we could choose how we shared and synced. The fact that it is even possible still seems like a bug to me.
I'm absolutely glad that the Shared vault can be set as the default one; it's great to be able to troubleshoot family members, check if 2FA is on, etc. without having to visit them in person and use their laptop.
Doesn't seem like a bug at all, and in fact I would likely switch to iCloud Keychain if this behavior went away (which doesn't support default-shared but is free).
There seem to be 2 problems here: Generate Password not telling you which vault it will be saved in, and the Shared vault being set as default (presumably) without user input.
In a tool like 1Password, they need to do enough to avoid user errors (I'm sure they are). That is the responsibility of these tools. In other words - there is no such thing as user errors for these tools.
