This seems pointless. There is no separate grant for just email vs. realname+email so you'll receive it whether you request it or not; making use of it by suggesting it as a default display name seems like the reasonable thing for the plugin to do when interfacing with a MediaWiki that has real names enabled.

I think what you really mean here is T151515: authonlyprivate OAuth grant should not mention real name when the wiki does not allow them which is a (fairly easy) MediaWiki-side development task.

@Tgr the developer has added a fix: "Prevent the realname property returned by wikimedia from being used in Discourse" and has also added additional text to the create account modal that allows anyone to input their realname/alternative name if they'd like.

We'd definitely be interested in making it so that this text doesn't include real name for Space.

It appears I should follow that up on T151515: authonlyprivate OAuth grant should not mention real name when the wiki does not allow them? Or is there something else you'd also recommend to attempt to modify that?

In T231879#5463341, @elappen-WMF wrote:

@Tgr the developer has added a fix: "Prevent the realname property returned by wikimedia from being used in Discourse" and has also added additional text to the create account modal that allows anyone to input their realname/alternative name if they'd like.

That doesn't fix any real problem we have and probably makes the plugin less useful for third parties.

It appears I should follow that up on T151515: authonlyprivate OAuth grant should not mention real name when the wiki does not allow them?

Yeah. That's a MediaWiki issue, there's nothing an OAuth application needing email addresses can do to affect it.