Ok, I've been able to find the other account in SSO that's associated with the gmail address (per Steve's comment above) and it does indeed have the OpenID identifier of the account in LP, which explains why it always thinks this user is connected with that email.
Ok, I've been able to find the other account in SSO that's associated with the gmail address (per Steve's comment above) and it does indeed have the OpenID identifier of the account in LP, which explains why it always thinks this user is connected with that email.