The blog feature on user profiles is still showing up with Delve disabled

I understand the reason, and want to make sure you are aware that the blogging component, surfaced on the Delve profile, is tied to the content management service of Office 365, supported by SharePoint Online. If you look at the URL strucuture, you'll notice it falls under a new site collection per user (ex: https://yourCompany.sharepoint.com/portals/hub/personal/yourAlias); meaning, a new internal personal blog post is in fact a SharePoint page (stored within a document library within the site colleciton I noted) that uses the new authoring canvas - same as Team News from within a modern team site. Note: a new blog can appear in the Delve feed alongside other types of content, but it's rooted in the same security and complioance of your customer's SharePoint Online environment.

Much of what is removed when you opt-out of Delve is any component of the service that use the Microsoft Graph - the intelligent layer in between users and the content/data that promote a more persoinalized experienece based on who users work with and what users work on. Once opted out, users will not see the Delve tile in the Office 365 app launcher, and various services that surface aspects of the Microsoft Graph to provide intelligence throughout Office 365 will simply not appear, or revert back to previous non-Graph-based methods - i.e. search-based vs graph-based. One example, if you opt out, you would not see the new "Discover" tab within OneDrive for Business - yet the core of OneDrive for Business remains intact.

Hope that help,

Mark