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Window Versus Tab

Chrome allows its users to open incognito windows, in which all tabs are
always incognito. There is no support for an incognito tab in a normal
window, and no support for a normal tab in an incognito window.

ScamBlockPlus displays untrusted websites on incognito tabs in normal windows,
only when they are opened by a click on a link in an email or by a click on a link
in a post or when opened by a website that is displayed on an incognito tab.

Forever Incognito

All tabs in an incognito Chrome window remain incognito until closed.
The incognito window also remains incognito until closed.

An incognito ScamBlockPlus tab remains incognito until the tab navigates to
a trusted website. When navigating to a trusted website the tab becomes an
ordinary tab (is no longer incognito).

Reading Emails & Incognito

Lets suppose that a user who owns a Gmail account wants to read emails inside an incognito window.
To do that the user must sign-into his/her Google account. The incognito window allows the user
to do that. When the user clicks on a scam-link in an email, a new tab is opened in which the fake
website is displayed. The fake page can request the user to login with Google. This can possibly cause
the Google account to be compromized. The conclusion is that incognito windows can't fully protect
Chrome users from phishing scams.
Note that Chrome users can request to open links, displayed inside normal windows, in new
incognito windows, but they don't know in advance if a link points to a trusted or untrusted
website. Additionally, a fake web-page displayed in an incognito window can still tempt the
user to input private details or to sign-into his/her Google account.

ScamBlockPlus incognito tabs are better for protecting Gmail users from phishing scams.
The user read emails in a normal window (which is not incognito). When the user clicks on a scam-link in
an email, the fake website is displayed in a new incognito tab. In that tab the user can't login with Google.